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Handle ands with 0 and shifts by 0 correctly. These aren't

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common, but indvars shouldn't crash on them. This fixes PR4054.

llvm-svn: 70051
This commit is contained in:
Dan Gohman 2009-04-25 17:05:40 +00:00
parent 285a5fb1d5
commit 9eb5ba6eb7
2 changed files with 32 additions and 2 deletions
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11
lib/Analysis/ScalarEvolution.cpp
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@ -1754,6 +1754,8 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) {
// For an expression like x&255 that merely masks off the high bits,
// use zext(trunc(x)) as the SCEV expression.
if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
if (CI->isNullValue())
return getSCEV(U->getOperand(1));
const APInt &A = CI->getValue();
unsigned Ones = A.countTrailingOnes();
if (APIntOps::isMask(Ones, A))
@ -1818,10 +1820,15 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) {
if (Instruction *L = dyn_cast<Instruction>(U->getOperand(0)))
if (L->getOpcode() == Instruction::Shl &&
L->getOperand(1) == U->getOperand(1)) {
uint64_t Amt = getTypeSizeInBits(U->getType()) - CI->getZExtValue();
unsigned BitWidth = getTypeSizeInBits(U->getType());
uint64_t Amt = BitWidth - CI->getZExtValue();
if (Amt == BitWidth)
return getSCEV(L->getOperand(0)); // shift by zero --> noop
if (Amt > BitWidth)
return getIntegerSCEV(0, U->getType()); // value is undefined
return
getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
IntegerType::get(Amt)),
IntegerType::get(Amt)),
U->getType());
}
break;

23
test/Transforms/IndVarSimplify/avoid-i0.ll Normal file
View File

@ -0,0 +1,23 @@
; RUN: llvm-as < %s | opt -indvars
; PR4054
; Don't treat an and with 0 as a mask (trunc+zext).
define i32 @int80(i8 signext %p_71) nounwind {
entry:
br label %bb
bb: ; preds = %bb6, %entry
%p_71_addr.0 = phi i8 [ %p_71, %entry ], [ %0, %bb6 ] ; <i8> [#uses=0]
br i1 false, label %bb4, label %bb1
bb1: ; preds = %bb
ret i32 0
bb4: ; preds = %bb4, %bb
br i1 false, label %bb6, label %bb4
bb6: ; preds = %bb4
%0 = and i8 0, 0 ; <i8> [#uses=1]
br label %bb
}