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llvm-project/llvm/test/CodeGen/X86/sink-local-value.ll

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[FastISel] Disable local value sinking by default This is causing compilation timeouts on code with long sequences of local values and calls (i.e. foo(1); foo(2); foo(3); ...). It turns out that code coverage instrumentation is a great way to create sequences like this, which how our users ran into the issue in practice. Intel has a tool that detects these kinds of non-linear compile time issues, and Andy Kaylor reported it as PR37010. The current sinking code scans the whole basic block once per local value sink, which happens before emitting each call. In theory, local values should only be introduced to be used by instructions between the current flush point and the last flush point, so we should only need to scan those instructions. llvm-svn: 329822
2018-04-12 00:03:07 +08:00
; RUN: llc -fast-isel-sink-local-values -O0 < %s | FileCheck %s
[FastISel] Sink local value materializations to first use Summary: Local values are constants, global addresses, and stack addresses that can't be folded into the instruction that uses them. For example, when storing the address of a global variable into memory, we need to materialize that address into a register. FastISel doesn't want to materialize any given local value more than once, so it generates all local value materialization code at EmitStartPt, which always dominates the current insertion point. This allows it to maintain a map of local value registers, and it knows that the local value area will always dominate the current insertion point. The downside is that local value instructions are always emitted without a source location. This is done to prevent jumpy line tables, but it means that the local value area will be considered part of the previous statement. Consider this C code: call1(); // line 1 ++global; // line 2 ++global; // line 3 call2(&global, &local); // line 4 Today we end up with assembly and line tables like this: .loc 1 1 callq call1 leaq global(%rip), %rdi leaq local(%rsp), %rsi .loc 1 2 addq $1, global(%rip) .loc 1 3 addq $1, global(%rip) .loc 1 4 callq call2 The LEA instructions in the local value area have no source location and are treated as being on line 1. Stepping through the code in a debugger and correlating it with the assembly won't make much sense, because these materializations are only required for line 4. This is actually problematic for the VS debugger "set next statement" feature, which effectively assumes that there are no registers live across statement boundaries. By sinking the local value code into the statement and fixing up the source location, we can make that feature work. This was filed as https://bugs.llvm.org/show_bug.cgi?id=35975 and https://crbug.com/793819. This change is obviously not enough to make this feature work reliably in all cases, but I felt that it was worth doing anyway because it usually generates smaller, more comprehensible -O0 code. I measured a 0.12% regression in code generation time with LLC on the sqlite3 amalgamation, so I think this is worth doing. There are some special cases worth calling out in the commit message: 1. local values materialized for phis 2. local values used by no-op casts 3. dead local value code Local values can be materialized for phis, and this does not show up as a vreg use in MachineRegisterInfo. In this case, if there are no other uses, this patch sinks the value to the first terminator, EH label, or the end of the BB if nothing else exists. Local values may also be used by no-op casts, which adds the register to the RegFixups table. Without reversing the RegFixups map direction, we don't have enough information to sink these instructions. Lastly, if the local value register has no other uses, we can delete it. This comes up when fastisel tries two instruction selection approaches and the first materializes the value but fails and the second succeeds without using the local value. Reviewers: aprantl, dblaikie, qcolombet, MatzeB, vsk, echristo Subscribers: dotdash, chandlerc, hans, sdardis, amccarth, javed.absar, zturner, llvm-commits, hiraditya Differential Revision: https://reviews.llvm.org/D43093 llvm-svn: 327581
2018-03-15 05:54:21 +08:00
target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
target triple = "i386-linux-gnu"
; Try some simple cases that show how local value sinking improves line tables.
@sink_across = external global i32
declare void @simple_callee(i32, i32)
define void @simple() !dbg !5 {
store i32 44, i32* @sink_across, !dbg !7
call void @simple_callee(i32 13, i32 55), !dbg !8
ret void, !dbg !9
}
; CHECK-LABEL: simple:
; CHECK-NOT: movl $13,
; CHECK: .loc 1 1 1 prologue_end
; CHECK: movl $44, sink_across
; CHECK: .loc 1 2 1
; CHECK: movl $13,
; CHECK: movl $55,
; CHECK: calll simple_callee
declare void @simple_reg_callee(i32 inreg, i32 inreg)
define void @simple_reg() !dbg !10 {
store i32 44, i32* @sink_across, !dbg !11
call void @simple_reg_callee(i32 inreg 13, i32 inreg 55), !dbg !12
ret void, !dbg !13
}
; CHECK-LABEL: simple_reg:
; CHECK: .loc 1 4 1 prologue_end
; CHECK: movl $44, sink_across
; CHECK: .loc 1 5 1
; CHECK: movl $13,
; CHECK: movl $55,
; CHECK: calll simple_reg_callee
; There are two interesting cases where local values have no uses but are not
; dead: when the local value is directly used by a phi, and when the local
; value is used by a no-op cast instruction. In these cases, we get side tables
; referring to the local value vreg that we need to check.
define i8* @phi_const(i32 %c) !dbg !14 {
entry:
%tobool = icmp eq i32 %c, 0, !dbg !20
call void @llvm.dbg.value(metadata i1 %tobool, metadata !16, metadata !DIExpression()), !dbg !20
br i1 %tobool, label %if.else, label %if.then, !dbg !21
if.then: ; preds = %entry
br label %if.end, !dbg !22
if.else: ; preds = %entry
br label %if.end, !dbg !23
if.end: ; preds = %if.else, %if.then
%r.0 = phi i8* [ inttoptr (i32 42 to i8*), %if.then ], [ inttoptr (i32 1 to i8*), %if.else ], !dbg !24
call void @llvm.dbg.value(metadata i8* %r.0, metadata !18, metadata !DIExpression()), !dbg !24
ret i8* %r.0, !dbg !25
}
; CHECK-LABEL: phi_const:
; CHECK: # %entry
; CHECK: cmpl $0,
; CHECK: # %if.then
; CHECK: movl $42,
; CHECK: jmp
; CHECK: # %if.else
; CHECK: movl $1,
; CHECK: # %if.end
define i8* @phi_const_cast(i32 %c) !dbg !26 {
entry:
%tobool = icmp eq i32 %c, 0, !dbg !32
call void @llvm.dbg.value(metadata i1 %tobool, metadata !28, metadata !DIExpression()), !dbg !32
br i1 %tobool, label %if.else, label %if.then, !dbg !33
if.then: ; preds = %entry
%v42 = inttoptr i32 42 to i8*, !dbg !34
call void @llvm.dbg.value(metadata i8* %v42, metadata !29, metadata !DIExpression()), !dbg !34
br label %if.end, !dbg !35
if.else: ; preds = %entry
%v1 = inttoptr i32 1 to i8*, !dbg !36
call void @llvm.dbg.value(metadata i8* %v1, metadata !30, metadata !DIExpression()), !dbg !36
br label %if.end, !dbg !37
if.end: ; preds = %if.else, %if.then
%r.0 = phi i8* [ %v42, %if.then ], [ %v1, %if.else ], !dbg !38
call void @llvm.dbg.value(metadata i8* %r.0, metadata !31, metadata !DIExpression()), !dbg !38
ret i8* %r.0, !dbg !39
}
; CHECK-LABEL: phi_const_cast:
; CHECK: # %entry
; CHECK: cmpl $0,
; CHECK: # %if.then
; CHECK: movl $42, %[[REG:[a-z]+]]
; CHECK: #DEBUG_VALUE: phi_const_cast:4 <- $[[REG]]
; CHECK: jmp
; CHECK: # %if.else
; CHECK: movl $1, %[[REG:[a-z]+]]
; CHECK: #DEBUG_VALUE: phi_const_cast:5 <- $[[REG]]
; CHECK: # %if.end
declare void @may_throw() local_unnamed_addr #1
declare i32 @__gxx_personality_v0(...)
define i32 @invoke_phi() personality i32 (...)* @__gxx_personality_v0 {
entry:
store i32 42, i32* @sink_across
invoke void @may_throw()
to label %try.cont unwind label %lpad
lpad: ; preds = %entry
%0 = landingpad { i8*, i32 }
catch i8* null
store i32 42, i32* @sink_across
br label %try.cont
try.cont: ; preds = %entry, %lpad
%r.0 = phi i32 [ 13, %entry ], [ 55, %lpad ]
ret i32 %r.0
}
; The constant materialization should be *after* the stores to sink_across, but
; before any EH_LABEL.
; CHECK-LABEL: invoke_phi:
; CHECK: movl $42, sink_across
; CHECK: movl $13, %{{[a-z]*}}
; CHECK: .Ltmp{{.*}}:
; CHECK: calll may_throw
; CHECK: .Ltmp{{.*}}:
; CHECK: jmp .LBB{{.*}}
; CHECK: .LBB{{.*}}: # %lpad
; CHECK: movl $42, sink_across
; CHECK: movl $55, %{{[a-z]*}}
; CHECK: .LBB{{.*}}: # %try.cont
; CHECK: retl
; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata) #0
attributes #0 = { nounwind readnone speculatable }
!llvm.dbg.cu = !{!0}
!llvm.debugify = !{!3, !4}
!llvm.module.flags = !{!52, !53}
!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "../llvm/test/CodeGen/X86/sink-local-value.ll", directory: "/")
!2 = !{}
!3 = !{i32 27}
!4 = !{i32 8}
[DebugInfo] Add DILabel metadata and intrinsic llvm.dbg.label. In order to set breakpoints on labels and list source code around labels, we need collect debug information for labels, i.e., label name, the function label belong, line number in the file, and the address label located. In order to keep these information in LLVM IR and to allow backend to generate debug information correctly. We create a new kind of metadata for labels, DILabel. The format of DILabel is !DILabel(scope: !1, name: "foo", file: !2, line: 3) We hope to keep debug information as much as possible even the code is optimized. So, we create a new kind of intrinsic for label metadata to avoid the metadata is eliminated with basic block. The intrinsic will keep existing if we keep it from optimized out. The format of the intrinsic is llvm.dbg.label(metadata !1) It has only one argument, that is the DILabel metadata. The intrinsic will follow the label immediately. Backend could get the label metadata through the intrinsic's parameter. We also create DIBuilder API for labels to be used by Frontend. Frontend could use createLabel() to allocate DILabel objects, and use insertLabel() to insert llvm.dbg.label intrinsic in LLVM IR. Differential Revision: https://reviews.llvm.org/D45024 Patch by Hsiangkai Wang. llvm-svn: 331841
2018-05-09 10:40:45 +08:00
!5 = distinct !DISubprogram(name: "simple", linkageName: "simple", scope: null, file: !1, line: 1, type: !6, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: true, unit: !0, retainedNodes: !2)
[FastISel] Sink local value materializations to first use Summary: Local values are constants, global addresses, and stack addresses that can't be folded into the instruction that uses them. For example, when storing the address of a global variable into memory, we need to materialize that address into a register. FastISel doesn't want to materialize any given local value more than once, so it generates all local value materialization code at EmitStartPt, which always dominates the current insertion point. This allows it to maintain a map of local value registers, and it knows that the local value area will always dominate the current insertion point. The downside is that local value instructions are always emitted without a source location. This is done to prevent jumpy line tables, but it means that the local value area will be considered part of the previous statement. Consider this C code: call1(); // line 1 ++global; // line 2 ++global; // line 3 call2(&global, &local); // line 4 Today we end up with assembly and line tables like this: .loc 1 1 callq call1 leaq global(%rip), %rdi leaq local(%rsp), %rsi .loc 1 2 addq $1, global(%rip) .loc 1 3 addq $1, global(%rip) .loc 1 4 callq call2 The LEA instructions in the local value area have no source location and are treated as being on line 1. Stepping through the code in a debugger and correlating it with the assembly won't make much sense, because these materializations are only required for line 4. This is actually problematic for the VS debugger "set next statement" feature, which effectively assumes that there are no registers live across statement boundaries. By sinking the local value code into the statement and fixing up the source location, we can make that feature work. This was filed as https://bugs.llvm.org/show_bug.cgi?id=35975 and https://crbug.com/793819. This change is obviously not enough to make this feature work reliably in all cases, but I felt that it was worth doing anyway because it usually generates smaller, more comprehensible -O0 code. I measured a 0.12% regression in code generation time with LLC on the sqlite3 amalgamation, so I think this is worth doing. There are some special cases worth calling out in the commit message: 1. local values materialized for phis 2. local values used by no-op casts 3. dead local value code Local values can be materialized for phis, and this does not show up as a vreg use in MachineRegisterInfo. In this case, if there are no other uses, this patch sinks the value to the first terminator, EH label, or the end of the BB if nothing else exists. Local values may also be used by no-op casts, which adds the register to the RegFixups table. Without reversing the RegFixups map direction, we don't have enough information to sink these instructions. Lastly, if the local value register has no other uses, we can delete it. This comes up when fastisel tries two instruction selection approaches and the first materializes the value but fails and the second succeeds without using the local value. Reviewers: aprantl, dblaikie, qcolombet, MatzeB, vsk, echristo Subscribers: dotdash, chandlerc, hans, sdardis, amccarth, javed.absar, zturner, llvm-commits, hiraditya Differential Revision: https://reviews.llvm.org/D43093 llvm-svn: 327581
2018-03-15 05:54:21 +08:00
!6 = !DISubroutineType(types: !2)
!7 = !DILocation(line: 1, column: 1, scope: !5)
!8 = !DILocation(line: 2, column: 1, scope: !5)
!9 = !DILocation(line: 3, column: 1, scope: !5)
[DebugInfo] Add DILabel metadata and intrinsic llvm.dbg.label. In order to set breakpoints on labels and list source code around labels, we need collect debug information for labels, i.e., label name, the function label belong, line number in the file, and the address label located. In order to keep these information in LLVM IR and to allow backend to generate debug information correctly. We create a new kind of metadata for labels, DILabel. The format of DILabel is !DILabel(scope: !1, name: "foo", file: !2, line: 3) We hope to keep debug information as much as possible even the code is optimized. So, we create a new kind of intrinsic for label metadata to avoid the metadata is eliminated with basic block. The intrinsic will keep existing if we keep it from optimized out. The format of the intrinsic is llvm.dbg.label(metadata !1) It has only one argument, that is the DILabel metadata. The intrinsic will follow the label immediately. Backend could get the label metadata through the intrinsic's parameter. We also create DIBuilder API for labels to be used by Frontend. Frontend could use createLabel() to allocate DILabel objects, and use insertLabel() to insert llvm.dbg.label intrinsic in LLVM IR. Differential Revision: https://reviews.llvm.org/D45024 Patch by Hsiangkai Wang. llvm-svn: 331841
2018-05-09 10:40:45 +08:00
!10 = distinct !DISubprogram(name: "simple_reg", linkageName: "simple_reg", scope: null, file: !1, line: 4, type: !6, isLocal: false, isDefinition: true, scopeLine: 4, isOptimized: true, unit: !0, retainedNodes: !2)
[FastISel] Sink local value materializations to first use Summary: Local values are constants, global addresses, and stack addresses that can't be folded into the instruction that uses them. For example, when storing the address of a global variable into memory, we need to materialize that address into a register. FastISel doesn't want to materialize any given local value more than once, so it generates all local value materialization code at EmitStartPt, which always dominates the current insertion point. This allows it to maintain a map of local value registers, and it knows that the local value area will always dominate the current insertion point. The downside is that local value instructions are always emitted without a source location. This is done to prevent jumpy line tables, but it means that the local value area will be considered part of the previous statement. Consider this C code: call1(); // line 1 ++global; // line 2 ++global; // line 3 call2(&global, &local); // line 4 Today we end up with assembly and line tables like this: .loc 1 1 callq call1 leaq global(%rip), %rdi leaq local(%rsp), %rsi .loc 1 2 addq $1, global(%rip) .loc 1 3 addq $1, global(%rip) .loc 1 4 callq call2 The LEA instructions in the local value area have no source location and are treated as being on line 1. Stepping through the code in a debugger and correlating it with the assembly won't make much sense, because these materializations are only required for line 4. This is actually problematic for the VS debugger "set next statement" feature, which effectively assumes that there are no registers live across statement boundaries. By sinking the local value code into the statement and fixing up the source location, we can make that feature work. This was filed as https://bugs.llvm.org/show_bug.cgi?id=35975 and https://crbug.com/793819. This change is obviously not enough to make this feature work reliably in all cases, but I felt that it was worth doing anyway because it usually generates smaller, more comprehensible -O0 code. I measured a 0.12% regression in code generation time with LLC on the sqlite3 amalgamation, so I think this is worth doing. There are some special cases worth calling out in the commit message: 1. local values materialized for phis 2. local values used by no-op casts 3. dead local value code Local values can be materialized for phis, and this does not show up as a vreg use in MachineRegisterInfo. In this case, if there are no other uses, this patch sinks the value to the first terminator, EH label, or the end of the BB if nothing else exists. Local values may also be used by no-op casts, which adds the register to the RegFixups table. Without reversing the RegFixups map direction, we don't have enough information to sink these instructions. Lastly, if the local value register has no other uses, we can delete it. This comes up when fastisel tries two instruction selection approaches and the first materializes the value but fails and the second succeeds without using the local value. Reviewers: aprantl, dblaikie, qcolombet, MatzeB, vsk, echristo Subscribers: dotdash, chandlerc, hans, sdardis, amccarth, javed.absar, zturner, llvm-commits, hiraditya Differential Revision: https://reviews.llvm.org/D43093 llvm-svn: 327581
2018-03-15 05:54:21 +08:00
!11 = !DILocation(line: 4, column: 1, scope: !10)
!12 = !DILocation(line: 5, column: 1, scope: !10)
!13 = !DILocation(line: 6, column: 1, scope: !10)
[DebugInfo] Add DILabel metadata and intrinsic llvm.dbg.label. In order to set breakpoints on labels and list source code around labels, we need collect debug information for labels, i.e., label name, the function label belong, line number in the file, and the address label located. In order to keep these information in LLVM IR and to allow backend to generate debug information correctly. We create a new kind of metadata for labels, DILabel. The format of DILabel is !DILabel(scope: !1, name: "foo", file: !2, line: 3) We hope to keep debug information as much as possible even the code is optimized. So, we create a new kind of intrinsic for label metadata to avoid the metadata is eliminated with basic block. The intrinsic will keep existing if we keep it from optimized out. The format of the intrinsic is llvm.dbg.label(metadata !1) It has only one argument, that is the DILabel metadata. The intrinsic will follow the label immediately. Backend could get the label metadata through the intrinsic's parameter. We also create DIBuilder API for labels to be used by Frontend. Frontend could use createLabel() to allocate DILabel objects, and use insertLabel() to insert llvm.dbg.label intrinsic in LLVM IR. Differential Revision: https://reviews.llvm.org/D45024 Patch by Hsiangkai Wang. llvm-svn: 331841
2018-05-09 10:40:45 +08:00
!14 = distinct !DISubprogram(name: "phi_const", linkageName: "phi_const", scope: null, file: !1, line: 7, type: !6, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: true, unit: !0, retainedNodes: !15)
[FastISel] Sink local value materializations to first use Summary: Local values are constants, global addresses, and stack addresses that can't be folded into the instruction that uses them. For example, when storing the address of a global variable into memory, we need to materialize that address into a register. FastISel doesn't want to materialize any given local value more than once, so it generates all local value materialization code at EmitStartPt, which always dominates the current insertion point. This allows it to maintain a map of local value registers, and it knows that the local value area will always dominate the current insertion point. The downside is that local value instructions are always emitted without a source location. This is done to prevent jumpy line tables, but it means that the local value area will be considered part of the previous statement. Consider this C code: call1(); // line 1 ++global; // line 2 ++global; // line 3 call2(&global, &local); // line 4 Today we end up with assembly and line tables like this: .loc 1 1 callq call1 leaq global(%rip), %rdi leaq local(%rsp), %rsi .loc 1 2 addq $1, global(%rip) .loc 1 3 addq $1, global(%rip) .loc 1 4 callq call2 The LEA instructions in the local value area have no source location and are treated as being on line 1. Stepping through the code in a debugger and correlating it with the assembly won't make much sense, because these materializations are only required for line 4. This is actually problematic for the VS debugger "set next statement" feature, which effectively assumes that there are no registers live across statement boundaries. By sinking the local value code into the statement and fixing up the source location, we can make that feature work. This was filed as https://bugs.llvm.org/show_bug.cgi?id=35975 and https://crbug.com/793819. This change is obviously not enough to make this feature work reliably in all cases, but I felt that it was worth doing anyway because it usually generates smaller, more comprehensible -O0 code. I measured a 0.12% regression in code generation time with LLC on the sqlite3 amalgamation, so I think this is worth doing. There are some special cases worth calling out in the commit message: 1. local values materialized for phis 2. local values used by no-op casts 3. dead local value code Local values can be materialized for phis, and this does not show up as a vreg use in MachineRegisterInfo. In this case, if there are no other uses, this patch sinks the value to the first terminator, EH label, or the end of the BB if nothing else exists. Local values may also be used by no-op casts, which adds the register to the RegFixups table. Without reversing the RegFixups map direction, we don't have enough information to sink these instructions. Lastly, if the local value register has no other uses, we can delete it. This comes up when fastisel tries two instruction selection approaches and the first materializes the value but fails and the second succeeds without using the local value. Reviewers: aprantl, dblaikie, qcolombet, MatzeB, vsk, echristo Subscribers: dotdash, chandlerc, hans, sdardis, amccarth, javed.absar, zturner, llvm-commits, hiraditya Differential Revision: https://reviews.llvm.org/D43093 llvm-svn: 327581
2018-03-15 05:54:21 +08:00
!15 = !{!16, !18}
!16 = !DILocalVariable(name: "1", scope: !14, file: !1, line: 7, type: !17)
!17 = !DIBasicType(name: "ty8", size: 8, encoding: DW_ATE_unsigned)
!18 = !DILocalVariable(name: "2", scope: !14, file: !1, line: 11, type: !19)
!19 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
!20 = !DILocation(line: 7, column: 1, scope: !14)
!21 = !DILocation(line: 8, column: 1, scope: !14)
!22 = !DILocation(line: 9, column: 1, scope: !14)
!23 = !DILocation(line: 10, column: 1, scope: !14)
!24 = !DILocation(line: 11, column: 1, scope: !14)
!25 = !DILocation(line: 12, column: 1, scope: !14)
[DebugInfo] Add DILabel metadata and intrinsic llvm.dbg.label. In order to set breakpoints on labels and list source code around labels, we need collect debug information for labels, i.e., label name, the function label belong, line number in the file, and the address label located. In order to keep these information in LLVM IR and to allow backend to generate debug information correctly. We create a new kind of metadata for labels, DILabel. The format of DILabel is !DILabel(scope: !1, name: "foo", file: !2, line: 3) We hope to keep debug information as much as possible even the code is optimized. So, we create a new kind of intrinsic for label metadata to avoid the metadata is eliminated with basic block. The intrinsic will keep existing if we keep it from optimized out. The format of the intrinsic is llvm.dbg.label(metadata !1) It has only one argument, that is the DILabel metadata. The intrinsic will follow the label immediately. Backend could get the label metadata through the intrinsic's parameter. We also create DIBuilder API for labels to be used by Frontend. Frontend could use createLabel() to allocate DILabel objects, and use insertLabel() to insert llvm.dbg.label intrinsic in LLVM IR. Differential Revision: https://reviews.llvm.org/D45024 Patch by Hsiangkai Wang. llvm-svn: 331841
2018-05-09 10:40:45 +08:00
!26 = distinct !DISubprogram(name: "phi_const_cast", linkageName: "phi_const_cast", scope: null, file: !1, line: 13, type: !6, isLocal: false, isDefinition: true, scopeLine: 13, isOptimized: true, unit: !0, retainedNodes: !27)
[FastISel] Sink local value materializations to first use Summary: Local values are constants, global addresses, and stack addresses that can't be folded into the instruction that uses them. For example, when storing the address of a global variable into memory, we need to materialize that address into a register. FastISel doesn't want to materialize any given local value more than once, so it generates all local value materialization code at EmitStartPt, which always dominates the current insertion point. This allows it to maintain a map of local value registers, and it knows that the local value area will always dominate the current insertion point. The downside is that local value instructions are always emitted without a source location. This is done to prevent jumpy line tables, but it means that the local value area will be considered part of the previous statement. Consider this C code: call1(); // line 1 ++global; // line 2 ++global; // line 3 call2(&global, &local); // line 4 Today we end up with assembly and line tables like this: .loc 1 1 callq call1 leaq global(%rip), %rdi leaq local(%rsp), %rsi .loc 1 2 addq $1, global(%rip) .loc 1 3 addq $1, global(%rip) .loc 1 4 callq call2 The LEA instructions in the local value area have no source location and are treated as being on line 1. Stepping through the code in a debugger and correlating it with the assembly won't make much sense, because these materializations are only required for line 4. This is actually problematic for the VS debugger "set next statement" feature, which effectively assumes that there are no registers live across statement boundaries. By sinking the local value code into the statement and fixing up the source location, we can make that feature work. This was filed as https://bugs.llvm.org/show_bug.cgi?id=35975 and https://crbug.com/793819. This change is obviously not enough to make this feature work reliably in all cases, but I felt that it was worth doing anyway because it usually generates smaller, more comprehensible -O0 code. I measured a 0.12% regression in code generation time with LLC on the sqlite3 amalgamation, so I think this is worth doing. There are some special cases worth calling out in the commit message: 1. local values materialized for phis 2. local values used by no-op casts 3. dead local value code Local values can be materialized for phis, and this does not show up as a vreg use in MachineRegisterInfo. In this case, if there are no other uses, this patch sinks the value to the first terminator, EH label, or the end of the BB if nothing else exists. Local values may also be used by no-op casts, which adds the register to the RegFixups table. Without reversing the RegFixups map direction, we don't have enough information to sink these instructions. Lastly, if the local value register has no other uses, we can delete it. This comes up when fastisel tries two instruction selection approaches and the first materializes the value but fails and the second succeeds without using the local value. Reviewers: aprantl, dblaikie, qcolombet, MatzeB, vsk, echristo Subscribers: dotdash, chandlerc, hans, sdardis, amccarth, javed.absar, zturner, llvm-commits, hiraditya Differential Revision: https://reviews.llvm.org/D43093 llvm-svn: 327581
2018-03-15 05:54:21 +08:00
!27 = !{!28, !29, !30, !31}
!28 = !DILocalVariable(name: "3", scope: !26, file: !1, line: 13, type: !17)
!29 = !DILocalVariable(name: "4", scope: !26, file: !1, line: 15, type: !19)
!30 = !DILocalVariable(name: "5", scope: !26, file: !1, line: 17, type: !19)
!31 = !DILocalVariable(name: "6", scope: !26, file: !1, line: 19, type: !19)
!32 = !DILocation(line: 13, column: 1, scope: !26)
!33 = !DILocation(line: 14, column: 1, scope: !26)
!34 = !DILocation(line: 15, column: 1, scope: !26)
!35 = !DILocation(line: 16, column: 1, scope: !26)
!36 = !DILocation(line: 17, column: 1, scope: !26)
!37 = !DILocation(line: 18, column: 1, scope: !26)
!38 = !DILocation(line: 19, column: 1, scope: !26)
!39 = !DILocation(line: 20, column: 1, scope: !26)
[DebugInfo] Add DILabel metadata and intrinsic llvm.dbg.label. In order to set breakpoints on labels and list source code around labels, we need collect debug information for labels, i.e., label name, the function label belong, line number in the file, and the address label located. In order to keep these information in LLVM IR and to allow backend to generate debug information correctly. We create a new kind of metadata for labels, DILabel. The format of DILabel is !DILabel(scope: !1, name: "foo", file: !2, line: 3) We hope to keep debug information as much as possible even the code is optimized. So, we create a new kind of intrinsic for label metadata to avoid the metadata is eliminated with basic block. The intrinsic will keep existing if we keep it from optimized out. The format of the intrinsic is llvm.dbg.label(metadata !1) It has only one argument, that is the DILabel metadata. The intrinsic will follow the label immediately. Backend could get the label metadata through the intrinsic's parameter. We also create DIBuilder API for labels to be used by Frontend. Frontend could use createLabel() to allocate DILabel objects, and use insertLabel() to insert llvm.dbg.label intrinsic in LLVM IR. Differential Revision: https://reviews.llvm.org/D45024 Patch by Hsiangkai Wang. llvm-svn: 331841
2018-05-09 10:40:45 +08:00
!40 = distinct !DISubprogram(name: "invoke_phi", linkageName: "invoke_phi", scope: null, file: !1, line: 21, type: !6, isLocal: false, isDefinition: true, scopeLine: 21, isOptimized: true, unit: !0, retainedNodes: !41)
[FastISel] Sink local value materializations to first use Summary: Local values are constants, global addresses, and stack addresses that can't be folded into the instruction that uses them. For example, when storing the address of a global variable into memory, we need to materialize that address into a register. FastISel doesn't want to materialize any given local value more than once, so it generates all local value materialization code at EmitStartPt, which always dominates the current insertion point. This allows it to maintain a map of local value registers, and it knows that the local value area will always dominate the current insertion point. The downside is that local value instructions are always emitted without a source location. This is done to prevent jumpy line tables, but it means that the local value area will be considered part of the previous statement. Consider this C code: call1(); // line 1 ++global; // line 2 ++global; // line 3 call2(&global, &local); // line 4 Today we end up with assembly and line tables like this: .loc 1 1 callq call1 leaq global(%rip), %rdi leaq local(%rsp), %rsi .loc 1 2 addq $1, global(%rip) .loc 1 3 addq $1, global(%rip) .loc 1 4 callq call2 The LEA instructions in the local value area have no source location and are treated as being on line 1. Stepping through the code in a debugger and correlating it with the assembly won't make much sense, because these materializations are only required for line 4. This is actually problematic for the VS debugger "set next statement" feature, which effectively assumes that there are no registers live across statement boundaries. By sinking the local value code into the statement and fixing up the source location, we can make that feature work. This was filed as https://bugs.llvm.org/show_bug.cgi?id=35975 and https://crbug.com/793819. This change is obviously not enough to make this feature work reliably in all cases, but I felt that it was worth doing anyway because it usually generates smaller, more comprehensible -O0 code. I measured a 0.12% regression in code generation time with LLC on the sqlite3 amalgamation, so I think this is worth doing. There are some special cases worth calling out in the commit message: 1. local values materialized for phis 2. local values used by no-op casts 3. dead local value code Local values can be materialized for phis, and this does not show up as a vreg use in MachineRegisterInfo. In this case, if there are no other uses, this patch sinks the value to the first terminator, EH label, or the end of the BB if nothing else exists. Local values may also be used by no-op casts, which adds the register to the RegFixups table. Without reversing the RegFixups map direction, we don't have enough information to sink these instructions. Lastly, if the local value register has no other uses, we can delete it. This comes up when fastisel tries two instruction selection approaches and the first materializes the value but fails and the second succeeds without using the local value. Reviewers: aprantl, dblaikie, qcolombet, MatzeB, vsk, echristo Subscribers: dotdash, chandlerc, hans, sdardis, amccarth, javed.absar, zturner, llvm-commits, hiraditya Differential Revision: https://reviews.llvm.org/D43093 llvm-svn: 327581
2018-03-15 05:54:21 +08:00
!41 = !{!42, !44}
!42 = !DILocalVariable(name: "7", scope: !40, file: !1, line: 23, type: !43)
!43 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_unsigned)
!44 = !DILocalVariable(name: "8", scope: !40, file: !1, line: 26, type: !19)
!45 = !DILocation(line: 21, column: 1, scope: !40)
!46 = !DILocation(line: 22, column: 1, scope: !40)
!47 = !DILocation(line: 23, column: 1, scope: !40)
!48 = !DILocation(line: 24, column: 1, scope: !40)
!49 = !DILocation(line: 25, column: 1, scope: !40)
!50 = !DILocation(line: 26, column: 1, scope: !40)
!51 = !DILocation(line: 27, column: 1, scope: !40)
!52 = !{i32 2, !"Dwarf Version", i32 4}
!53 = !{i32 2, !"Debug Info Version", i32 3}