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make truncate/sext elimination capable of changing phi's. This

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implements rdar://6013816 and the testcase in Transforms/InstCombine/sext-misc.ll.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52440 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-06-18 04:00:49 +00:00
parent fab8387384
commit 8114b718c9
2 changed files with 50 additions and 7 deletions
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40
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -6838,6 +6838,16 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
///
/// This is a truncation operation if Ty is smaller than V->getType(), or an
/// extension operation if Ty is larger.
///
/// If CastOpc is a truncation, then Ty will be a type smaller than V. We
/// should return true if trunc(V) can be computed by computing V in the smaller
/// type. If V is an instruction, then trunc(inst(x,y)) can be computed as
/// inst(trunc(x),trunc(y)), which only makes sense if x and y can be
/// efficiently truncated.
///
/// If CastOpc is a sext or zext, we are asking if the low bits of the value can
/// bit computed in a larger type, which is then and'd or sext_in_reg'd to get
/// the final result.
bool InstCombiner::CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
unsigned CastOpc,
int &NumCastsRemoved) {
@ -6858,7 +6868,7 @@ bool InstCombiner::CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
// If the first operand is itself a cast, and is eliminable, do not count
// this as an eliminable cast. We would prefer to eliminate those two
// casts first.
if (!isa<CastInst>(I->getOperand(0)))
if (!isa<CastInst>(I->getOperand(0)) && I->hasOneUse())
++NumCastsRemoved;
return true;
}
@ -6923,8 +6933,17 @@ bool InstCombiner::CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
// of casts in the input.
if (I->getOpcode() == CastOpc)
return true;
break;
case Instruction::PHI: {
// We can change a phi if we can change all operands.
PHINode *PN = cast<PHINode>(I);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (!CanEvaluateInDifferentType(PN->getIncomingValue(i), Ty, CastOpc,
NumCastsRemoved))
return false;
return true;
}
default:
// TODO: Can handle more cases here.
break;
@ -6957,7 +6976,7 @@ Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
Res = BinaryOperator::Create((Instruction::BinaryOps)I->getOpcode(),
LHS, RHS, I->getName());
LHS, RHS);
break;
}
case Instruction::Trunc:
@ -6969,16 +6988,27 @@ Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
if (I->getOperand(0)->getType() == Ty)
return I->getOperand(0);
// Otherwise, must be the same type of case, so just reinsert a new one.
// Otherwise, must be the same type of cast, so just reinsert a new one.
Res = CastInst::Create(cast<CastInst>(I)->getOpcode(), I->getOperand(0),
Ty, I->getName());
Ty);
break;
case Instruction::PHI: {
PHINode *OPN = cast<PHINode>(I);
PHINode *NPN = PHINode::Create(Ty);
for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) {
Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned);
NPN->addIncoming(V, OPN->getIncomingBlock(i));
}
Res = NPN;
break;
}
default:
// TODO: Can handle more cases here.
assert(0 && "Unreachable!");
break;
}
Res->takeName(I);
return InsertNewInstBefore(Res, *I);
}

17
test/Transforms/InstCombine/sext-misc.ll
View File

@ -1,6 +1,4 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep sext
; RUN: llvm-as < %s | llc -march=x86-64 | not grep movslq
; RUN: llvm-as < %s | llc -march=x86 | not grep sar
declare i32 @llvm.ctpop.i32(i32)
declare i32 @llvm.ctlz.i32(i32)
@ -50,3 +48,18 @@ define i32 @woo(i8 %a, i32 %f, i1 %p, i32* %z) {
%n = sext i16 %s to i32
ret i32 %n
}
; rdar://6013816
define i16 @test(i16 %t, i1 %cond) nounwind {
entry:
br i1 %cond, label %T, label %F
T:
%t2 = sext i16 %t to i32
br label %F
F:
%V = phi i32 [%t2, %T], [42, %entry]
%W = trunc i32 %V to i16
ret i16 %W
}