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Implement PR2206.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49967 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-04-19 22:17:26 +00:00
parent 1c14c29746
commit d881ad2c57
2 changed files with 21 additions and 8 deletions
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25
lib/VMCore/ConstantFold.cpp
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@ -548,8 +548,8 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
if (CI2->isAllOnesValue())
return const_cast<Constant*>(C1); // X & -1 == X
// (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
// (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
if (CE1->getOpcode() == Instruction::ZExt) {
unsigned DstWidth = CI2->getType()->getBitWidth();
unsigned SrcWidth =
@ -559,16 +559,25 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
return const_cast<Constant*>(C1);
}
// If and'ing the address of a global with a constant, fold it.
if (CE1->getOpcode() == Instruction::PtrToInt &&
isa<GlobalValue>(CE1->getOperand(0))) {
GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
// Functions are at least 4-byte aligned. If and'ing the address of a
// function with a constant < 4, fold it to zero.
if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
isa<Function>(CPR))
return Constant::getNullValue(CI->getType());
// Functions are at least 4-byte aligned.
unsigned GVAlign = GV->getAlignment();
if (isa<Function>(GV))
GVAlign = std::max(GVAlign, 4U);
if (GVAlign > 1) {
unsigned DstWidth = CI2->getType()->getBitWidth();
unsigned SrcWidth = std::min(SrcWidth, Log2_32(GVAlign));
APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
// If checking bits we know are clear, return zero.
if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
return Constant::getNullValue(CI2->getType());
}
}
}
break;

4
test/Assembler/ConstantExprFold.llx
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@ -24,3 +24,7 @@ global i1 icmp slt (i32* getelementptr (%Ty* @B, i64 0, i32 0),
i32* getelementptr (%Ty* @B, i64 0, i32 1)) ; true
;global i1 icmp ne (i64* @A, i64* bitcast (%Ty* @B to i64*)) ; true
; PR2206
@cons = weak global i32 0, align 8 ; <i32*> [#uses=1]
global i64 and (i64 ptrtoint (i32* @cons to i64), i64 7)