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NewGVN: Fix PR32403 - Handling of undef in phis was not quite correct

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due to LLVM's view of phi nodes.  It would cause NewGVN not to fixpoint
in some interesting edge cases.

llvm-svn: 298687
This commit is contained in:
Daniel Berlin 2017-03-24 05:30:34 +00:00
parent b3d605ee1f
commit 9f0bf61efa
2 changed files with 79 additions and 1 deletions
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15
lib/Transforms/Scalar/NewGVN.cpp
View File

@ -368,6 +368,7 @@ private:
const Expression *performSymbolicPredicateInfoEvaluation(Instruction *);
// Congruence finding.
bool someEquivalentDominates(const Instruction *, const Instruction *) const;
Value *lookupOperandLeader(Value *) const;
void performCongruenceFinding(Instruction *, const Expression *);
void moveValueToNewCongruenceClass(Instruction *, CongruenceClass *,
@ -724,6 +725,18 @@ const CallExpression *NewGVN::createCallExpression(CallInst *CI,
return E;
}
// Return true if some equivalent of instruction Inst dominates instruction U.
bool NewGVN::someEquivalentDominates(const Instruction *Inst,
const Instruction *U) const {
auto *CC = ValueToClass.lookup(Inst);
assert(isa<Instruction>(CC->RepLeader) && CC->RepLeader == Inst);
if (CC)
return llvm::any_of(CC->Members, [&](const Value *Member) {
return DT->dominates(cast<Instruction>(Member), U);
});
return false;
}
// See if we have a congruence class and leader for this operand, and if so,
// return it. Otherwise, return the operand itself.
Value *NewGVN::lookupOperandLeader(Value *V) const {
@ -1054,7 +1067,7 @@ const Expression *NewGVN::performSymbolicPHIEvaluation(Instruction *I) {
if (HasUndef) {
// Only have to check for instructions
if (auto *AllSameInst = dyn_cast<Instruction>(AllSameValue))
if (!DT->dominates(AllSameInst, I))
if (!someEquivalentDominates(AllSameInst, I))
return E;
}

65
test/Transforms/NewGVN/pr32403.ll Normal file
View File

@ -0,0 +1,65 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
;RUN: opt -newgvn -S < %s | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.12.0"
; Function Attrs: nounwind ssp uwtable
define void @reorder_ref_pic_list() local_unnamed_addr {
; CHECK-LABEL: @reorder_ref_pic_list(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 undef, label [[FOR_END:%.*]], label [[FOR_BODY_PREHEADER:%.*]]
; CHECK: for.body.preheader:
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[REFIDXLX_0:%.*]] = phi i32 [ [[INC_I51:%.*]], [[IF_ELSE58:%.*]] ], [ 0, [[FOR_BODY_PREHEADER]] ]
; CHECK-NEXT: br i1 undef, label [[IF_THEN13:%.*]], label [[IF_ELSE58]]
; CHECK: if.then13:
; CHECK-NEXT: [[INC_I:%.*]] = add nsw i32 [[REFIDXLX_0]], 1
; CHECK-NEXT: br label [[FOR_BODY8_I:%.*]]
; CHECK: for.body8.i:
; CHECK-NEXT: br i1 undef, label [[FOR_INC24_I:%.*]], label [[IF_THEN17_I:%.*]]
; CHECK: if.then17.i:
; CHECK-NEXT: br label [[FOR_INC24_I]]
; CHECK: for.inc24.i:
; CHECK-NEXT: br label [[FOR_BODY8_I]]
; CHECK: if.else58:
; CHECK-NEXT: [[INC_I51]] = add nsw i32 [[REFIDXLX_0]], 1
; CHECK-NEXT: br label [[FOR_BODY]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br i1 undef, label %for.end, label %for.body.preheader
for.body.preheader: ; preds = %entry
br label %for.body
for.body: ; preds = %if.else58, %for.body.preheader
%refIdxLX.0 = phi i32 [ %inc.i51, %if.else58 ], [ 0, %for.body.preheader ]
br i1 undef, label %if.then13, label %if.else58
if.then13: ; preds = %for.body
%inc.i = add nsw i32 %refIdxLX.0, 1
br label %for.body8.i
for.body8.i: ; preds = %for.inc24.i, %if.then13
%nIdx.052.i = phi i32 [ %inc.i, %if.then13 ], [ %nIdx.1.i, %for.inc24.i ]
br i1 undef, label %for.inc24.i, label %if.then17.i
if.then17.i: ; preds = %for.body8.i
br label %for.inc24.i
for.inc24.i: ; preds = %if.then17.i, %for.body8.i
%nIdx.1.i = phi i32 [ undef, %if.then17.i ], [ %nIdx.052.i, %for.body8.i ]
br label %for.body8.i
if.else58: ; preds = %for.body
%inc.i51 = add nsw i32 %refIdxLX.0, 1
br label %for.body
for.end: ; preds = %entry
ret void
}