maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/test/CodeGen/AArch64/switch-unreachable-default.ll

98 lines
2.2 KiB
LLVM
Raw Normal View History

Re-commit r355490 "[CodeGen] Omit range checks from jump tables when lowering switches with unreachable default" Original commit by Ayonam Ray. This commit adds a regression test for the issue discovered in the previous commit: that the range check for the jump table can only be omitted if the fall-through destination of the jump table is unreachable, which isn't necessarily true just because the default of the switch is unreachable. This addresses the missing optimization in PR41242. > During the lowering of a switch that would result in the generation of a > jump table, a range check is performed before indexing into the jump > table, for the switch value being outside the jump table range and a > conditional branch is inserted to jump to the default block. In case the > default block is unreachable, this conditional jump can be omitted. This > patch implements omitting this conditional branch for unreachable > defaults. > > Differential Revision: https://reviews.llvm.org/D52002 > Reviewers: Hans Wennborg, Eli Freidman, Roman Lebedev llvm-svn: 357067
2019-03-27 22:10:11 +08:00
; RUN: llc -O3 -o - %s | FileCheck %s
; Test that the output in the presence of an unreachable default does not have
; a compare and branch at the top of the switch to handle the default case.
target triple = "aarch64-unknown-linux-gnu"
; Function Attrs: nounwind
define void @fn(i4) {
switch i4 %0, label %default [
i4 0, label %case_0
i4 1, label %case_1
i4 2, label %case_2
i4 3, label %case_3
i4 4, label %case_4
i4 5, label %case_5
]
; CHECK-LABEL: fn:
; CHECK-NOT: sub
; CHECK-NOT: cmp
; CHECK-NOT: b.hi
; CHECK: ldrb {{w[0-9]+}}, [{{x[0-9]+}}, {{x[0-9]+}}]
; CHECK: add {{x[0-9]+}}, {{x[0-9]+}}, {{x[0-9]+}}, lsl #2
; CHECK: br {{x[0-9]+}}
default:
unreachable
case_0:
tail call void @handle_case_00(i4 %0) #2
br label %return_label
case_1:
tail call void @handle_case_01(i4 %0) #2
br label %return_label
case_2:
tail call void @handle_case_02(i4 %0) #2
br label %return_label
case_3:
tail call void @handle_case_03(i4 %0) #2
br label %return_label
case_4:
tail call void @handle_case_04(i4 %0) #2
br label %return_label
case_5:
tail call void @handle_case_05(i4 %0) #2
br label %return_label
return_label:
ret void
}
declare void @handle_case_00(i4)
declare void @handle_case_01(i4)
declare void @handle_case_02(i4)
declare void @handle_case_03(i4)
declare void @handle_case_04(i4)
declare void @handle_case_05(i4)
define i32 @reachable_fallthrough(i32 %x) {
entry:
switch i32 %x, label %def [
i32 1, label %bb1
i32 8, label %bb2
i32 16, label %bb3
i32 32, label %bb4
i32 64, label %bb5
]
Switch lowering: exploit unreachable fall-through when lowering case range cluster In the example below, we would previously emit two range checks, one for cases 1--3 and one for 4--6. This patch makes us exploit the fact that the fall-through is unreachable and only one range check is necessary. switch i32 %i, label %default [ i32 1, label %bb1 i32 2, label %bb1 i32 3, label %bb1 i32 4, label %bb2 i32 5, label %bb2 i32 6, label %bb2 ] default: unreachable llvm-svn: 357252
2019-03-29 21:40:05 +08:00
; The switch is lowered with a jump table for cases 1--32 and case 64 handled
; separately. Even though the default of the switch is unreachable, the
; fall-through for the jump table *is* reachable so the range check must be
; emitted.
Re-commit r355490 "[CodeGen] Omit range checks from jump tables when lowering switches with unreachable default" Original commit by Ayonam Ray. This commit adds a regression test for the issue discovered in the previous commit: that the range check for the jump table can only be omitted if the fall-through destination of the jump table is unreachable, which isn't necessarily true just because the default of the switch is unreachable. This addresses the missing optimization in PR41242. > During the lowering of a switch that would result in the generation of a > jump table, a range check is performed before indexing into the jump > table, for the switch value being outside the jump table range and a > conditional branch is inserted to jump to the default block. In case the > default block is unreachable, this conditional jump can be omitted. This > patch implements omitting this conditional branch for unreachable > defaults. > > Differential Revision: https://reviews.llvm.org/D52002 > Reviewers: Hans Wennborg, Eli Freidman, Roman Lebedev llvm-svn: 357067
2019-03-27 22:10:11 +08:00
;
; CHECK-LABEL: reachable_fallthrough
Switch lowering: exploit unreachable fall-through when lowering case range cluster In the example below, we would previously emit two range checks, one for cases 1--3 and one for 4--6. This patch makes us exploit the fact that the fall-through is unreachable and only one range check is necessary. switch i32 %i, label %default [ i32 1, label %bb1 i32 2, label %bb1 i32 3, label %bb1 i32 4, label %bb2 i32 5, label %bb2 i32 6, label %bb2 ] default: unreachable llvm-svn: 357252
2019-03-29 21:40:05 +08:00
; CHECK: sub [[REG:w[0-9]+]], w0, #1
; CHECK: cmp [[REG]], #31
Re-commit r355490 "[CodeGen] Omit range checks from jump tables when lowering switches with unreachable default" Original commit by Ayonam Ray. This commit adds a regression test for the issue discovered in the previous commit: that the range check for the jump table can only be omitted if the fall-through destination of the jump table is unreachable, which isn't necessarily true just because the default of the switch is unreachable. This addresses the missing optimization in PR41242. > During the lowering of a switch that would result in the generation of a > jump table, a range check is performed before indexing into the jump > table, for the switch value being outside the jump table range and a > conditional branch is inserted to jump to the default block. In case the > default block is unreachable, this conditional jump can be omitted. This > patch implements omitting this conditional branch for unreachable > defaults. > > Differential Revision: https://reviews.llvm.org/D52002 > Reviewers: Hans Wennborg, Eli Freidman, Roman Lebedev llvm-svn: 357067
2019-03-27 22:10:11 +08:00
; CHECK: b.hi
def: unreachable
bb1: br label %return
bb2: br label %return
bb3: br label %return
bb4: br label %return
bb5: br label %return
return:
Switch lowering: exploit unreachable fall-through when lowering case range cluster In the example below, we would previously emit two range checks, one for cases 1--3 and one for 4--6. This patch makes us exploit the fact that the fall-through is unreachable and only one range check is necessary. switch i32 %i, label %default [ i32 1, label %bb1 i32 2, label %bb1 i32 3, label %bb1 i32 4, label %bb2 i32 5, label %bb2 i32 6, label %bb2 ] default: unreachable llvm-svn: 357252
2019-03-29 21:40:05 +08:00
%p = phi i32 [ 3, %bb1 ], [ 2, %bb2 ], [ 1, %bb3 ], [ 0, %bb4 ], [ 42, %bb5 ]
Re-commit r355490 "[CodeGen] Omit range checks from jump tables when lowering switches with unreachable default" Original commit by Ayonam Ray. This commit adds a regression test for the issue discovered in the previous commit: that the range check for the jump table can only be omitted if the fall-through destination of the jump table is unreachable, which isn't necessarily true just because the default of the switch is unreachable. This addresses the missing optimization in PR41242. > During the lowering of a switch that would result in the generation of a > jump table, a range check is performed before indexing into the jump > table, for the switch value being outside the jump table range and a > conditional branch is inserted to jump to the default block. In case the > default block is unreachable, this conditional jump can be omitted. This > patch implements omitting this conditional branch for unreachable > defaults. > > Differential Revision: https://reviews.llvm.org/D52002 > Reviewers: Hans Wennborg, Eli Freidman, Roman Lebedev llvm-svn: 357067
2019-03-27 22:10:11 +08:00
ret i32 %p
}