33146857e9
This adjusts mayHaveSideEffect() to return true for !willReturn() instructions. Just like other side-effects, non-willreturn calls (aka "divergence") cannot be removed and cannot be reordered relative to other side effects. This fixes a number of bugs where non-willreturn calls are either incorrectly dropped or moved. In particular, it also fixes the last open problem in https://bugs.llvm.org/show_bug.cgi?id=50511. I performed a cursory review of all current mayHaveSideEffect() uses, which convinced me that these are indeed the desired default semantics. Places that do not want to consider non-willreturn as a sideeffect generally do not want mayHaveSideEffect() semantics at all. I identified two such cases, which are addressed by D106591 and D106742. Finally, there is a use in SCEV for which we don't really have an appropriate API right now -- what it wants is basically "would this be considered forward progress". I've just spelled out the previous semantics there. Differential Revision: https://reviews.llvm.org/D106749
45 lines
1.3 KiB
LLVM
45 lines
1.3 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -sccp -loop-deletion -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
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declare double @sqrt(double) readnone nounwind willreturn
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%empty = type {}
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declare %empty @has_side_effects()
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; No matter how hard you try, sqrt(1.0) is always 1.0. This allows the
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; optimizer to delete this loop.
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define double @test_0(i32 %param) {
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; CHECK-LABEL: @test_0(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: ret double 1.000000e+00
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;
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entry:
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br label %Loop
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Loop: ; preds = %Loop, %entry
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%I2 = phi i32 [ 0, %entry ], [ %I3, %Loop ]
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%V = phi double [ 1.000000e+00, %entry ], [ %V2, %Loop ]
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%V2 = call double @sqrt( double %V )
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%I3 = add i32 %I2, 1
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%tmp.7 = icmp ne i32 %I3, %param
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br i1 %tmp.7, label %Loop, label %Exit
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Exit: ; preds = %Loop
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ret double %V
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}
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define i32 @test_1() {
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; CHECK-LABEL: @test_1(
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; CHECK-NEXT: [[TMP1:%.*]] = call [[EMPTY:%.*]] @has_side_effects()
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; CHECK-NEXT: ret i32 0
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;
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%1 = call %empty @has_side_effects()
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ret i32 0
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}
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define i32 @test_not_willreturn() {
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; CHECK-LABEL: @test_not_willreturn(
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; CHECK-NEXT: [[TMP1:%.*]] = call [[EMPTY:%.*]] @has_side_effects() #[[ATTR1:[0-9]+]]
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; CHECK-NEXT: ret i32 0
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;
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%1 = call %empty @has_side_effects() nounwind readonly
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ret i32 0
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}
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