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[InstCombine] Avoid creating mis-sized dbg.values in commonCastTransforms() 

This prevents InstCombine from creating mis-sized dbg.values when
replacing a sequence of casts with a simpler cast. For example, in:

  (fptrunc (floor (fpext X))) -> (floorf X)

We no longer emit dbg.value(X) (with a 32-bit float operand) to describe
(fpext X) (which is a 64-bit float).

This was diagnosed by the debugify check added in r335682.

llvm-svn: 335696
This commit is contained in:
Vedant Kumar 2018-06-27 00:47:53 +00:00
parent d13536e9f3
commit f6c0b41fb7
2 changed files with 8 additions and 2 deletions
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7
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -266,10 +266,13 @@ Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
if (Instruction::CastOps NewOpc = isEliminableCastPair(CSrc, &CI)) {
// The first cast (CSrc) is eliminable so we need to fix up or replace
// the second cast (CI). CSrc will then have a good chance of being dead.
auto *Res = CastInst::Create(NewOpc, CSrc->getOperand(0), CI.getType());
auto *Ty = CI.getType();
auto *Res = CastInst::Create(NewOpc, CSrc->getOperand(0), Ty);
// Replace debug users of the eliminable cast by emitting debug values
// which refer to the new cast.
insertReplacementDbgValues(*CSrc, *Res, *std::next(CI.getIterator()));
if (Ty->isIntegerTy() || Ty->isPointerTy())
// TODO: Support floats and vectors (see DW_OP_convert, fragment).
insertReplacementDbgValues(*CSrc, *Res, *std::next(CI.getIterator()));
return Res;
}
}

3
llvm/test/Transforms/InstCombine/double-float-shrink-2.ll
View File

@ -5,6 +5,7 @@
; RUN: opt < %s -instcombine -S -mtriple "i386-pc-mingw32" | FileCheck -check-prefix=ALL -check-prefix=DO-SIMPLIFY %s
; RUN: opt < %s -instcombine -S -mtriple "x86_64-pc-mingw32" | FileCheck -check-prefix=ALL -check-prefix=DO-SIMPLIFY %s
; RUN: opt < %s -instcombine -S -mtriple "sparc-sun-solaris" | FileCheck -check-prefix=ALL -check-prefix=DO-SIMPLIFY %s
; RUN: opt < %s -enable-debugify -instcombine -S -mtriple "x86_64-pc-win32" 2>&1 | FileCheck -check-prefix=DBG-VALID %s
declare double @floor(double)
declare double @ceil(double)
@ -685,3 +686,5 @@ define float @test_no_shrink_intrin_fabs_multi_use_fpext(half %C) {
%F = fptrunc double %E to float
ret float %F
}
; DBG-VALID: CheckModuleDebugify: PASS