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4395c8f610
Salvaging a redundant load instruction into a debug expression hides a memory read from optimisation passes. Passes that alter memory behaviour (such as LICM promoting memory to a register) aren't aware of these debug memory reads and leave them unaltered, making the debug variable location point somewhere unsafe. Teaching passes to know about these debug memory reads would be challenging and probably incomplete. Finding dbg.value instructions that need to be fixed would likely be computationally expensive too, as more analysis would be required. It's better to not generate debug-memory-reads instead, alas. Changed tests: * DeadStoreElim: test for salvaging of intermediate operations contributing to the dead store, instead of salvaging of the redundant load, * GVN: remove debuginfo behaviour checks completely, this behaviour is still covered by other tests, * InstCombine: don't test for salvaged loads, we're removing that behaviour. Differential Revision: https://reviews.llvm.org/D57962 llvm-svn: 353824
32 lines
1.1 KiB
LLVM
32 lines
1.1 KiB
LLVM
; RUN: opt < %s -debugify -basicaa -dse -S | FileCheck %s
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target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
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declare noalias i8* @malloc(i32)
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declare void @test_f()
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define i32* @test_salvage(i32 %arg) {
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; Check that all four original local variables have their values preserved.
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; CHECK-LABEL: @test_salvage(
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; CHECK-NEXT: malloc
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; CHECK-NEXT: @llvm.dbg.value(metadata i8* %p, metadata ![[p:.*]], metadata !DIExpression())
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; CHECK-NEXT: bitcast
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; CHECK-NEXT: @llvm.dbg.value(metadata i32* %P, metadata ![[P:.*]], metadata !DIExpression())
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; CHECK-NEXT: @llvm.dbg.value(metadata i32 %arg, metadata ![[DEAD:.*]], metadata !DIExpression(DW_OP_plus_uconst, 1, DW_OP_stack_value))
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; CHECK-NEXT: call void @test_f()
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; CHECK-NEXT: store i32 0, i32* %P
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%p = tail call i8* @malloc(i32 4)
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%P = bitcast i8* %p to i32*
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%DEAD = add i32 %arg, 1
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store i32 %DEAD, i32* %P
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call void @test_f()
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store i32 0, i32* %P
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ret i32* %P
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}
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; CHECK: ![[p]] = !DILocalVariable(name: "1"
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; CHECK: ![[P]] = !DILocalVariable(name: "2"
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; CHECK: ![[DEAD]] = !DILocalVariable(name: "3"
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