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[DebugInfo][InstCombine] Preserve DI after combining zext

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When zext is EvaluatedInDifferentType, InstCombine
drops the dbg.value intrinsic. This patch tries to
preserve said DI, by inserting the zext's old DI in the
resulting instruction. (Only for integer type for now)

Differential Revision: https://reviews.llvm.org/D48331

llvm-svn: 336254
This commit is contained in:
Anastasis Grammenos 2018-07-04 09:55:46 +00:00
parent 900e069df2
commit 72ae081881
2 changed files with 22 additions and 2 deletions
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11
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -1079,6 +1079,17 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
Value *Res = EvaluateInDifferentType(Src, DestTy, false);
assert(Res->getType() == DestTy);
// When DestTy is integer, try to preserve any debug values referring
// to the zext being replaced.
// TODO: This should work for vectors as well, possibly via the use
// of DWARF fragments.
if (DestTy->isIntegerTy()) {
insertReplacementDbgValues(
*Src, *Res, CI, [](DbgInfoIntrinsic &OldDII) -> DIExpression * {
return OldDII.getExpression();
});
}
uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear;
uint32_t DestBitSize = DestTy->getScalarSizeInBits();

13
test/Transforms/InstCombine/cast-mul-select.ll
View File

@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
; RUN: opt -debugify -instcombine -S < %s | FileCheck %s -check-prefix DBGINFO
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32"
@ -8,7 +8,16 @@ define i32 @mul(i32 %x, i32 %y) {
; CHECK-NEXT: [[C:%.*]] = mul i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[D:%.*]] = and i32 [[C]], 255
; CHECK-NEXT: ret i32 [[D]]
;
; Test that when zext is evaluated in different type
; we preserve the debug information in the resulting
; instruction.
; DBGINFO-LABEL: @mul(
; DBGINFO-NEXT: [[C:%.*]] = mul i32 {{.*}}
; DBGINFO-NEXT: call void @llvm.dbg.value(metadata i32 [[C]]
; DBGINFO-NEXT: [[D:%.*]] = and i32 {{.*}}
; DBGINFO-NEXT: call void @llvm.dbg.value(metadata i32 [[D]]
%A = trunc i32 %x to i8
%B = trunc i32 %y to i8
%C = mul i8 %A, %B