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[LoopStrengthReduce] Ensure that debug intrinsics do not affect LSR's output 

During Loop Strength Reduce, if the terminating condition for the loop
is not immediately adjacent to the terminating branch and it has more
than one use, a clone of the condition will be created just before the
terminating branch and will be used as the branch condition. Currently,
whether the instructions are "immediately adjacent" is determined by
checking whether the next instruction after the condition is the
terminating branch; this is incorrect however, as the presence of a
debug intrinsic between the two will result in a change to the output.
This is fixed by using getNextNonDebugInstruction() instead.

Differential Revision: https://reviews.llvm.org/D103033
This commit is contained in:
Stephen Tozer 2021-05-27 17:03:32 +01:00
parent 476e4d65d4
commit 4316b0e59c
2 changed files with 94 additions and 1 deletions
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2
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -2477,7 +2477,7 @@ LSRInstance::OptimizeLoopTermCond() {
// It's possible for the setcc instruction to be anywhere in the loop, and
// possible for it to have multiple users. If it is not immediately before
// the exiting block branch, move it.
if (&*++BasicBlock::iterator(Cond) != TermBr) {
if (Cond->getNextNonDebugInstruction() != TermBr) {
if (Cond->hasOneUse()) {
Cond->moveBefore(TermBr);
} else {

93
llvm/test/Transforms/LoopStrengthReduce/X86/lsr-cond-dbg.ll Normal file
View File

@ -0,0 +1,93 @@
; RUN: opt -S -loop-reduce < %s | FileCheck %s
; During Loop Strength Reduce, if the terminating condition for the loop is not
; immediately adjacent to the terminating branch and it has more than one use,
; a clone of the condition will be created just before the terminating branch
; and will be used as the branch condition.
; The purpose of this test is to check that the presence of a debug intrinsic
; between the condition and branch does not trigger this behaviour, as this
; would cause debug info to affect CodeGen.
; CHECK-LABEL: i:
; CHECK-NOT: icmp
; CHECK: [[COND:%.*]] = icmp eq i8
; CHECK-NEXT: call void @llvm.dbg.value(metadata i1 [[COND]]
; CHECK-NEXT: br i1 [[COND]]
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@b = dso_local local_unnamed_addr global i8 0, align 1, !dbg !0
@a = dso_local local_unnamed_addr global i32 0, align 4, !dbg !6
@c = dso_local local_unnamed_addr global i8 0, align 1, !dbg !9
define dso_local signext i16 @d() local_unnamed_addr !dbg !17 {
entry:
%0 = load i32, i32* @a, align 4
%tobool2.not = icmp eq i32 %0, 0
%1 = load i8, i8* @b, align 1, !dbg !24
%cmp.not13 = icmp eq i8 %1, 7, !dbg !24
br i1 %cmp.not13, label %cleanup, label %if.end.preheader, !dbg !24
if.end.preheader: ; preds = %entry
br label %if.end, !dbg !24
if.end: ; preds = %if.end.preheader, %i
%2 = phi i8 [ %add, %i ], [ %1, %if.end.preheader ]
br i1 %tobool2.not, label %i, label %if.end4, !dbg !24
if.end4: ; preds = %if.end
%conv5 = trunc i32 %0 to i16, !dbg !24
br label %cleanup, !dbg !24
i: ; preds = %if.end
%add = add i8 %2, 1, !dbg !24
store i8 %add, i8* @b, align 1, !dbg !24
%cmp.not = icmp eq i8 %add, 7, !dbg !24
call void @llvm.dbg.value(metadata i1 %cmp.not, metadata !23, metadata !DIExpression(DW_OP_LLVM_convert, 1, DW_ATE_unsigned, DW_OP_LLVM_convert, 32, DW_ATE_unsigned, DW_OP_stack_value)), !dbg !24
br i1 %cmp.not, label %cleanup.loopexit, label %if.end, !dbg !24
cleanup.loopexit: ; preds = %i
br label %cleanup
cleanup: ; preds = %cleanup.loopexit, %if.end4, %entry
%cmp.not12 = phi i1 [ %cmp.not13, %if.end4 ], [ %cmp.not13, %entry ], [ %cmp.not, %cleanup.loopexit ]
%retval.0 = phi i16 [ %conv5, %if.end4 ], [ undef, %entry ], [ undef, %cleanup.loopexit ]
%3 = load i8, i8* @c, align 1
%conv8 = sext i8 %3 to i16
%retval.1 = select i1 %cmp.not12, i16 %conv8, i16 %retval.0
ret i16 %retval.1, !dbg !24
}
declare void @llvm.dbg.value(metadata, metadata, metadata)
!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!12, !13, !14, !15}
!llvm.ident = !{!16}
!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !3, line: 2, type: !11, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 13.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, splitDebugInlining: false, nameTableKind: None)
!3 = !DIFile(filename: "lsr-cond-dbg.c", directory: "/")
!4 = !{}
!5 = !{!6, !0, !9}
!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
!7 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !8, isLocal: false, isDefinition: true)
!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!9 = !DIGlobalVariableExpression(var: !10, expr: !DIExpression())
!10 = distinct !DIGlobalVariable(name: "c", scope: !2, file: !3, line: 2, type: !11, isLocal: false, isDefinition: true)
!11 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
!12 = !{i32 7, !"Dwarf Version", i32 4}
!13 = !{i32 2, !"Debug Info Version", i32 3}
!14 = !{i32 1, !"wchar_size", i32 4}
!15 = !{i32 7, !"uwtable", i32 1}
!16 = !{!"clang version 13.0.0"}
!17 = distinct !DISubprogram(name: "d", scope: !3, file: !3, line: 3, type: !18, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !21)
!18 = !DISubroutineType(types: !19)
!19 = !{!20}
!20 = !DIBasicType(name: "short", size: 16, encoding: DW_ATE_signed)
!21 = !{!23}
!22 = distinct !DILexicalBlock(scope: !17, file: !3, line: 4, column: 3)
!23 = !DILocalVariable(name: "g", scope: !22, file: !3, line: 7, type: !8)
!24 = !DILocation(line: 5, column: 9, scope: !22)