llvm-project/llvm/lib/Transforms
Bjorn Pettersson 8dd6cf711f [DebugInfo] Corrections for salvageDebugInfo
Summary:
When salvaging a dbg.declare/dbg.addr we should not add
DW_OP_stack_value to the DIExpression
(see test/Transforms/InstCombine/salvage-dbg-declare.ll).

Consider this example
  %vla = alloca i32, i64 2
  call void @llvm.dbg.declare(metadata i32* %vla, metadata !1, metadata !DIExpression())

Instcombine will turn it into
  %vla1 = alloca [2 x i32]
  %vla1.sub = getelementptr inbounds [2 x i32], [2 x i32]* %vla, i64 0, i64 0
  call void @llvm.dbg.declare(metadata [2 x i32]* %vla1.sub, metadata !19, metadata !DIExpression())

If the GEP can be eliminated, then the dbg.declare will be salvaged
and we should get
  %vla1 = alloca [2 x i32]
  call void @llvm.dbg.declare(metadata [2 x i32]* %vla1, metadata !19, metadata !DIExpression())

The problem was that salvageDebugInfo did not recognize dbg.declare
as being indirect (%vla1 points to the value, it does not hold the
value), so we incorrectly got
  call void @llvm.dbg.declare(metadata [2 x i32]* %vla1, metadata !19, metadata !DIExpression(DW_OP_stack_value))

I also made sure that llvm::salvageDebugInfo and
DIExpression::prependOpcodes do not add DW_OP_stack_value to
the DIExpression in case no new operands are added to the
DIExpression. That way we avoid to, unneccessarily, turn a
register location expression into an implicit location expression
in some situations (see test11 in test/Transforms/LICM/sinking.ll).

Reviewers: aprantl, vsk

Reviewed By: aprantl, vsk

Subscribers: JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D48837

llvm-svn: 336191
2018-07-03 11:29:00 +00:00
..
AggressiveInstCombine Move Analysis/Utils/Local.h back to Transforms 2018-06-04 21:23:21 +00:00
Coroutines Move Analysis/Utils/Local.h back to Transforms 2018-06-04 21:23:21 +00:00
Hello
IPO [UnrollAndJam] New Unroll and Jam pass 2018-07-01 12:47:30 +00:00
InstCombine [InstCombine] Delay foldICmpUsingKnownBits until simple transforms are done 2018-07-03 06:23:57 +00:00
Instrumentation [HWASan] Do not retag allocas before return from the function. 2018-06-29 20:20:17 +00:00
ObjCARC ProvenanceAnalysis: Store WeakTrackingVH instead of Value* in UnderlyingValue Cache. 2018-06-21 05:14:00 +00:00
Scalar [PM/LoopUnswitch] Fix PR37651 by correctly invalidating SCEV when 2018-07-03 09:13:27 +00:00
Utils [DebugInfo] Corrections for salvageDebugInfo 2018-07-03 11:29:00 +00:00
Vectorize [SLP] Recognize min/max pattern using instructions producing same values. 2018-07-02 17:55:31 +00:00
CMakeLists.txt Another try to commit 323321 (aggressive instruction combine). 2018-01-25 12:06:32 +00:00
LLVMBuild.txt Another try to commit 323321 (aggressive instruction combine). 2018-01-25 12:06:32 +00:00