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[Debug] Add dbg.value intrinsics for PHIs created during LCSSA.

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Summary:
This patch is an enhancement to propagate dbg.value information when Phis are created on behalf of LCSSA.
I noticed a case where a value carried across a loop was reported as <optimized out>.

Specifically this case:
```
int bar(int x, int y) {
  return x + y;
}

int foo(int size) {
  int val = 0;
  for (int i = 0; i < size; ++i) {
    val = bar(val, i);  // Both val and i are correct
  }
  return val; // <optimized out>
}
```

In the above case, after all of the interesting computation completes our value
is reported as "optimized out." This change will add a dbg.value to correct this.

This patch also moves the dbg.value insertion routine from LoopRotation.cpp 
into Local.cpp, so that we can share it in both places (LoopRotation and LCSSA).

Reviewers: mzolotukhin, aprantl, vsk, davide

Reviewed By: aprantl, vsk

Subscribers: dberlin, llvm-commits

Differential Revision: https://reviews.llvm.org/D42551

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325926 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matt Davis 2018-02-23 17:38:27 +00:00
parent 6ed382f4f6
commit 799e36774a
4 changed files with 147 additions and 8 deletions
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9
lib/Transforms/Utils/LCSSA.cpp
View File

@ -43,6 +43,7 @@
#include "llvm/IR/PredIteratorCache.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
@ -214,11 +215,15 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
Worklist.push_back(PostProcessPN);
// Keep track of PHI nodes that we want to remove because they did not have
// any uses rewritten.
// any uses rewritten. If the new PHI is used, store it so that we can
// try to propagate dbg.value intrinsics to it.
SmallVector<PHINode *, 2> NeedDbgValues;
for (PHINode *PN : AddedPHIs)
if (PN->use_empty())
PHIsToRemove.insert(PN);
else
NeedDbgValues.push_back(PN);
insertDebugValuesForPHIs(InstBB, NeedDbgValues);
Changed = true;
}
// Remove PHI nodes that did not have any uses rewritten.

7
lib/Transforms/Utils/Local.cpp
View File

@ -1365,14 +1365,17 @@ void llvm::insertDebugValuesForPHIs(BasicBlock *BB,
// propagate the info through the new PHI.
LLVMContext &C = BB->getContext();
for (auto PHI : InsertedPHIs) {
BasicBlock *Parent = PHI->getParent();
// Avoid inserting an intrinsic into an EH block.
if (Parent->getFirstNonPHI()->isEHPad())
continue;
auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI));
for (auto VI : PHI->operand_values()) {
auto V = DbgValueMap.find(VI);
if (V != DbgValueMap.end()) {
auto *DbgII = cast<DbgInfoIntrinsic>(V->second);
Instruction *NewDbgII = DbgII->clone();
auto PhiMAV = MetadataAsValue::get(C, ValueAsMetadata::get(PHI));
NewDbgII->setOperand(0, PhiMAV);
BasicBlock *Parent = PHI->getParent();
auto InsertionPt = Parent->getFirstInsertionPt();
assert(InsertionPt != Parent->end() && "Ill-formed basic block");
NewDbgII->insertBefore(&*InsertionPt);

133
test/Transforms/LCSSA/avoid-intrinsics-in-catchswitch.ll Normal file
View File

@ -0,0 +1,133 @@
; RUN: opt < %s -debugify -licm -S 1>/dev/null
;
; The following test is from https://bugs.llvm.org/show_bug.cgi?id=36238
; This test should pass (not assert or fault). The error that originally
; provoked this test was regarding the LCSSA pass trying to insert a dbg.value
; intrinsic into a catchswitch block.
target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-windows-msvc19.11.0"
%struct.e = type { i32 }
%struct.d = type { i8 }
%class.f = type { %class.b }
%class.b = type { i8 }
%struct.k = type opaque
@"\01?l@@3HA" = local_unnamed_addr global i32 0, align 4
define i32 @"\01?m@@YAJXZ"() personality i8* bitcast (i32 (...)* @__C_specific_handler to i8*) {
entry:
%n = alloca %struct.e, align 4
%db = alloca i32, align 4
%o = alloca %struct.d, align 1
%q = alloca i8*, align 8
%r = alloca i32, align 4
%u = alloca i64, align 8
%s = alloca %class.f, align 1
%offset = alloca i64, align 8
%t = alloca i64, align 8
%status = alloca i32, align 4
call void (...) @llvm.localescape(%class.f* nonnull %s, i32* nonnull %status)
%0 = bitcast %struct.e* %n to i8*
%1 = bitcast i32* %db to i8*
%2 = getelementptr inbounds %struct.d, %struct.d* %o, i64 0, i32 0
%3 = bitcast i8** %q to i8*
%4 = bitcast i32* %r to i8*
%5 = bitcast i64* %u to i8*
%6 = getelementptr inbounds %class.f, %class.f* %s, i64 0, i32 0, i32 0
%7 = load i32, i32* @"\01?l@@3HA", align 4, !tbaa !3
%call = call %class.f* @"\01??0f@@QEAA@H@Z"(%class.f* nonnull %s, i32 %7)
%8 = bitcast i64* %offset to i8*
%9 = bitcast i64* %t to i8*
%10 = bitcast i32* %status to i8*
%11 = bitcast %class.f* %s to %struct.d*
%c = getelementptr inbounds %struct.e, %struct.e* %n, i64 0, i32 0
br label %for.cond
for.cond: ; preds = %cleanup.cont, %entry
%p.0 = phi i32 [ undef, %entry ], [ %call2, %cleanup.cont ]
invoke void @"\01?h@@YAXPEAH0HPEAIPEAPEAEPEA_K33PEAUd@@4@Z"(i32* nonnull %db, i32* nonnull %c, i32 undef, i32* nonnull %r, i8** nonnull %q, i64* nonnull %u, i64* nonnull %offset, i64* nonnull %t, %struct.d* nonnull %11, %struct.d* nonnull %o)
to label %__try.cont unwind label %catch.dispatch
catch.dispatch: ; preds = %for.cond
%12 = catchswitch within none [label %__except.ret] unwind label %ehcleanup
__except.ret: ; preds = %catch.dispatch
%13 = catchpad within %12 [i8* bitcast (i32 (i8*, i8*)* @"\01?filt$0@0@m@@" to i8*)]
catchret from %13 to label %cleanup7
__try.cont: ; preds = %for.cond
%tobool = icmp eq i32 %p.0, 0
br i1 %tobool, label %if.end, label %cleanup7
if.end: ; preds = %__try.cont
%call2 = invoke i32 @"\01?a@@YAJXZ"()
to label %cleanup.cont unwind label %ehcleanup
cleanup.cont: ; preds = %if.end
br label %for.cond
ehcleanup: ; preds = %if.end, %catch.dispatch
%14 = cleanuppad within none []
%g.i = getelementptr inbounds %class.f, %class.f* %s, i64 0, i32 0
call void @"\01??1b@@QEAA@XZ"(%class.b* nonnull %g.i) [ "funclet"(token %14) ]
cleanupret from %14 unwind to caller
cleanup7: ; preds = %__try.cont, %__except.ret
%p.2.ph = phi i32 [ 7, %__except.ret ], [ %p.0, %__try.cont ]
%g.i32 = getelementptr inbounds %class.f, %class.f* %s, i64 0, i32 0
call void @"\01??1b@@QEAA@XZ"(%class.b* nonnull %g.i32)
ret i32 %p.2.ph
}
declare %class.f* @"\01??0f@@QEAA@H@Z"(%class.f* returned, i32) unnamed_addr
define internal i32 @"\01?filt$0@0@m@@"(i8* %exception_pointers, i8* %frame_pointer) personality i8* bitcast (i32 (...)* @__C_specific_handler to i8*) {
entry:
%0 = tail call i8* @llvm.x86.seh.recoverfp(i8* bitcast (i32 ()* @"\01?m@@YAJXZ" to i8*), i8* %frame_pointer)
%1 = tail call i8* @llvm.localrecover(i8* bitcast (i32 ()* @"\01?m@@YAJXZ" to i8*), i8* %0, i32 0)
%2 = tail call i8* @llvm.localrecover(i8* bitcast (i32 ()* @"\01?m@@YAJXZ" to i8*), i8* %0, i32 1)
%status = bitcast i8* %2 to i32*
%agg.tmp = alloca %class.f, align 1
%3 = bitcast i8* %exception_pointers to i32**
%4 = load i32*, i32** %3, align 8
%5 = load i32, i32* %4, align 4
%6 = bitcast i8* %exception_pointers to %struct.k*
%7 = getelementptr inbounds %class.f, %class.f* %agg.tmp, i64 0, i32 0, i32 0
%8 = load i8, i8* %1, align 1
store i8 %8, i8* %7, align 1
%call = invoke i32 @"\01?j@@YAJVf@@JPEAUk@@PEAH@Z"(i8 %8, i32 %5, %struct.k* %6, i32* %status)
to label %invoke.cont unwind label %ehcleanup
invoke.cont: ; preds = %entry
%g.i = getelementptr inbounds %class.f, %class.f* %agg.tmp, i64 0, i32 0
call void @"\01??1b@@QEAA@XZ"(%class.b* nonnull %g.i)
ret i32 %call
ehcleanup: ; preds = %entry
%9 = cleanuppad within none []
%g.i2 = getelementptr inbounds %class.f, %class.f* %agg.tmp, i64 0, i32 0
call void @"\01??1b@@QEAA@XZ"(%class.b* nonnull %g.i2) [ "funclet"(token %9) ]
cleanupret from %9 unwind to caller
}
declare i8* @llvm.x86.seh.recoverfp(i8*, i8*)
declare i8* @llvm.localrecover(i8*, i8*, i32)
declare i32 @"\01?j@@YAJVf@@JPEAUk@@PEAH@Z"(i8, i32, %struct.k*, i32*) local_unnamed_addr
declare i32 @__C_specific_handler(...)
declare void @"\01?h@@YAXPEAH0HPEAIPEAPEAEPEA_K33PEAUd@@4@Z"(i32*, i32*, i32, i32*, i8**, i64*, i64*, i64*, %struct.d*, %struct.d*) local_unnamed_addr
declare i32 @"\01?a@@YAJXZ"() local_unnamed_addr
declare void @llvm.localescape(...)
declare void @"\01??1b@@QEAA@XZ"(%class.b*) unnamed_addr
!llvm.module.flags = !{!0, !1}
!llvm.ident = !{!2}
!0 = !{i32 1, !"wchar_size", i32 2}
!1 = !{i32 7, !"PIC Level", i32 2}
!2 = !{!"clang"}
!3 = !{!4, !4, i64 0}
!4 = !{!"int", !5, i64 0}
!5 = !{!"omnipotent char", !6, i64 0}
!6 = !{!"Simple C++ TBAA"}

6
test/Transforms/LCSSA/basictest.ll
View File

@ -1,5 +1,6 @@
; RUN: opt < %s -lcssa -S | FileCheck %s
; RUN: opt < %s -passes=lcssa -S | FileCheck %s
; RUN: opt < %s -debugify -lcssa -S | FileCheck -check-prefix=CHECK2 %s
define void @lcssa(i1 %S2) {
; CHECK-LABEL: @lcssa
@ -18,11 +19,8 @@ post.if: ; preds = %if.false, %if.true
br i1 %S2, label %loop.exit, label %loop.interior
loop.exit: ; preds = %post.if
; CHECK: %X3.lcssa = phi i32
; CHECK: %X4 = add i32 3, %X3.lcssa
; CHECK2: call void @llvm.dbg.value(metadata i32 %X3.lcssa, metadata !11, metadata !DIExpression()), !dbg !19
; CHECK2-NEXT: add i32 3, %X3.lcssa
; CHECK2: ret void
; CHECK: %X4 = add i32 3, %X3.lcssa
%X4 = add i32 3, %X3 ; <i32> [#uses=0]
ret void
}