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Fix PR5262: when folding select into PHI, make sure all operands are available

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in the PHI's Basic Block. This uses a conservative approach, because we don't
have dominator info in instcombine.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84754 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Torok Edwin 2009-10-21 10:49:00 +00:00
parent 4e4bba5c80
commit 0739bd0ab2
3 changed files with 169 additions and 6 deletions
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66
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -1985,6 +1985,42 @@ static Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
return 0;
}
// Check whether all the operands of the PHI dominate the PHI node,
// knowing that the PHI's operands either dominate BB, or are defined in the BB.
static bool checkPHI(PHINode *PN, BasicBlock *BB)
{
BasicBlock *phiBB = PN->getParent();
for (unsigned i=0;i<PN->getNumIncomingValues();i++) {
Instruction *I = dyn_cast<Instruction>(PN->getIncomingValue(i));
if (!I)
continue;
BasicBlock *pBB = I->getParent();
if (pBB == BB) {
// another PHI in same BB is always before PN (PN is last phi).
if (isa<PHINode>(I))
continue;
// An instruction in the same BB, and not a phi, this is after PN.
return false;
}
if (phiBB == BB)
continue;
// We don't have dominator info, so just check that the instruction
// is not defined in on of the BB on the unique path between BB and phiBB.
// If there is no such unique path, or pBB equals to one of the BBs on that
// path we know that this operand doesn't dominate the PHI node.
BasicBlock *B = PN->getIncomingBlock(i);
while ((B = B->getUniquePredecessor())) {
if (pBB == B)
return false;
if (B == phiBB)
break;
}
// No unique path -> doesn't dominate
if (!B)
return false;
}
return true;
}
/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which
/// has a PHI node as operand #0, see if we can fold the instruction into the
@ -2036,9 +2072,13 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
// Okay, we can do the transformation: create the new PHI node.
PHINode *NewPN = PHINode::Create(I.getType(), "");
NewPN->reserveOperandSpace(PN->getNumOperands()/2);
InsertNewInstBefore(NewPN, *PN);
NewPN->takeName(PN);
// We must the PHI node as the last PHI, because it may use one of the other
// PHIs.
BasicBlock::iterator BBIt = PN;
while (isa<PHINode>(BBIt)) ++BBIt;
InsertNewInstBefore(NewPN, *BBIt);
SmallVector<Instruction*, 2> tmpWorklist;
// Next, add all of the operands to the PHI.
if (SelectInst *SI = dyn_cast<SelectInst>(&I)) {
// We only currently try to fold the condition of a select when it is a phi,
@ -2058,7 +2098,7 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
InV = SelectInst::Create(PN->getIncomingValue(i), TrueVInPred,
FalseVInPred,
"phitmp", NonConstBB->getTerminator());
Worklist.Add(cast<Instruction>(InV));
tmpWorklist.push_back(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, ThisBB);
}
@ -2084,8 +2124,7 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
NonConstBB->getTerminator());
else
llvm_unreachable("Unknown binop!");
Worklist.Add(cast<Instruction>(InV));
tmpWorklist.push_back(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
@ -2101,11 +2140,26 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
InV = CastInst::Create(CI->getOpcode(), PN->getIncomingValue(i),
I.getType(), "phitmp",
NonConstBB->getTerminator());
Worklist.Add(cast<Instruction>(InV));
tmpWorklist.push_back(cast<Instruction>(InV));
}
NewPN->addIncoming(InV, PN->getIncomingBlock(i));
}
}
// The PHI's operands must dominate the PHI, if we can't prove that
// undo this transformation.
if (!checkPHI(NewPN, I.getParent())) {
Worklist.Remove(NewPN);
NewPN->eraseFromParent();
while (!tmpWorklist.empty()) {
tmpWorklist.pop_back_val()->eraseFromParent();
}
return 0;
}
while (!tmpWorklist.empty()) {
Worklist.Add(tmpWorklist.pop_back_val());
}
NewPN->takeName(PN);
Worklist.Add(PN);
return ReplaceInstUsesWith(I, NewPN);
}

55
test/Transforms/InstCombine/crash.ll
View File

@ -44,3 +44,58 @@ entry:
store i32 %ins, i32* %arrayidx20
ret void
}
; PR5262
@tmp2 = global i64 0 ; <i64*> [#uses=1]
declare void @use(i64) nounwind
define void @foo(i1) nounwind align 2 {
; <label>:1
br i1 %0, label %2, label %3
; <label>:2 ; preds = %1
br label %3
; <label>:3 ; preds = %2, %1
%4 = phi i8 [ 1, %2 ], [ 0, %1 ] ; <i8> [#uses=1]
%5 = icmp eq i8 %4, 0 ; <i1> [#uses=1]
%6 = load i64* @tmp2, align 8 ; <i64> [#uses=1]
%7 = select i1 %5, i64 0, i64 %6 ; <i64> [#uses=1]
br label %8
; <label>:8 ; preds = %3
call void @use(i64 %7)
ret void
}
%t0 = type { i32, i32 }
%t1 = type { i32, i32, i32, i32, i32* }
declare %t0* @bar2(i64)
define void @bar3(i1, i1) nounwind align 2 {
; <label>:2
br i1 %1, label %10, label %3
; <label>:3 ; preds = %2
%4 = getelementptr inbounds %t0* null, i64 0, i32 1 ; <i32*> [#uses=0]
%5 = getelementptr inbounds %t1* null, i64 0, i32 4 ; <i32**> [#uses=1]
%6 = load i32** %5, align 8 ; <i32*> [#uses=1]
%7 = icmp ne i32* %6, null ; <i1> [#uses=1]
%8 = zext i1 %7 to i32 ; <i32> [#uses=1]
%9 = add i32 %8, 0 ; <i32> [#uses=1]
br label %10
; <label>:10 ; preds = %3, %2
%11 = phi i32 [ %9, %3 ], [ 0, %2 ] ; <i32> [#uses=1]
br i1 %1, label %12, label %13
; <label>:12 ; preds = %10
br label %13
; <label>:13 ; preds = %12, %10
%14 = zext i32 %11 to i64 ; <i64> [#uses=1]
%15 = tail call %t0* @bar2(i64 %14) nounwind ; <%0*> [#uses=0]
ret void
}

54
test/Transforms/InstCombine/fold-intophi.ll Normal file
View File

@ -0,0 +1,54 @@
; RUN: opt -instcombine -S <%s | FileCheck %s
; PR5262
; Make sure the PHI node gets put in a place where all of its operands dominate it
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"
target triple = "x86_64-unknown-linux-gnu"
@tmp2 = global i64 0 ; <i64*> [#uses=1]
declare void @use(i64) nounwind
define void @foo(i1) nounwind align 2 {
; <label>:1
br i1 %0, label %2, label %3
; <label>:2 ; preds = %1
br label %3
; <label>:3 ; preds = %2, %1
; CHECK: <label>:3
; CHECK-NEXT: %v4 = phi i1 [ false, %2 ], [ true, %1 ]
; CHECK-NEXT: %v4_ = phi i1 [ true, %2 ], [ false, %1 ]
; CHECK-NEXT: br label %l8
%v4 = phi i8 [ 1, %2 ], [ 0, %1 ] ; <i8> [#uses=1]
%v4_ = phi i8 [ 0, %2 ], [ 1, %1 ] ; <i8> [#uses=1]
%v5 = icmp eq i8 %v4, 0 ; <i1> [#uses=1]
%v5_ = icmp eq i8 %v4_, 0 ; <i1> [#uses=1]
%v6 = load i64* @tmp2, align 8 ; <i64> [#uses=1]
%v7 = select i1 %v5, i64 0, i64 %v6 ; <i64> [#uses=1]
br label %l8
l8:
%v9 = load i64* @tmp2, align 8
call void @use(i64 %v7)
br label %l10
l10:
%v11 = select i1 %v5_, i64 0, i64 %v9 ; <i64> [#uses=1]
call void @use(i64 %v11)
br label %l11
l11:
%v12 = load i64* @tmp2, align 8
%v13 = select i1 %v5_, i64 0, i64 %v12 ; <i64> [#uses=1]
call void @use(i64 %v13)
br i1 %0, label %l12, label %l13
l12:
br label %l13
l13:
;CHECK: l13:
;CHECK-NEXT: %v14 = phi i64 [ %v12, %l12 ], [ 0, %l11 ]
;CHECK-NEXT: call void @use(i64 %v14)
%v14 = phi i1 [0, %l12], [1, %l11]
%v16 = select i1 %v14, i64 0, i64 %v12 ; <i64> [#uses=1]
call void @use(i64 %v16)
ret void
}