[llvm-commits] [llvm] r102042 - in /llvm/trunk: lib/Analysis/ScalarEvolution.cpp test/Analysis/ScalarEvolution/undefined.ll
Dan Gohman
gohman at apple.com
Wed Apr 21 18:35:12 PDT 2010
Author: djg
Date: Wed Apr 21 20:35:11 2010
New Revision: 102042
URL: http://llvm.org/viewvc/llvm-project?rev=102042&view=rev
Log:
Don't attempt to analyze values which are obviously undef. This fixes some
assertion failures in extreme cases.
Added:
llvm/trunk/test/Analysis/ScalarEvolution/undefined.ll
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=102042&r1=102041&r2=102042&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Wed Apr 21 20:35:11 2010
@@ -1846,77 +1846,81 @@
if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
if (RHSC->getValue()->equalsInt(1))
return LHS; // X udiv 1 --> x
- if (RHSC->getValue()->isZero())
- return getIntegerSCEV(0, LHS->getType()); // value is undefined
-
- // Determine if the division can be folded into the operands of
- // its operands.
- // TODO: Generalize this to non-constants by using known-bits information.
- const Type *Ty = LHS->getType();
- unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
- unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ;
- // For non-power-of-two values, effectively round the value up to the
- // nearest power of two.
- if (!RHSC->getValue()->getValue().isPowerOf2())
- ++MaxShiftAmt;
- const IntegerType *ExtTy =
- IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
- // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
- if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
- if (const SCEVConstant *Step =
- dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
- if (!Step->getValue()->getValue()
- .urem(RHSC->getValue()->getValue()) &&
- getZeroExtendExpr(AR, ExtTy) ==
- getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
- getZeroExtendExpr(Step, ExtTy),
- AR->getLoop())) {
- SmallVector<const SCEV *, 4> Operands;
- for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
- Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
- return getAddRecExpr(Operands, AR->getLoop());
- }
- // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
- if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
- SmallVector<const SCEV *, 4> Operands;
- for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
- Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
- if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
- // Find an operand that's safely divisible.
- for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
- const SCEV *Op = M->getOperand(i);
- const SCEV *Div = getUDivExpr(Op, RHSC);
- if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
- Operands = SmallVector<const SCEV *, 4>(M->op_begin(), M->op_end());
- Operands[i] = Div;
- return getMulExpr(Operands);
+ // If the denominator is zero, the result of the udiv is undefined. Don't
+ // try to analyze it, because the resolution chosen here may differ from
+ // the resolution chosen in other parts of the compiler.
+ if (!RHSC->getValue()->isZero()) {
+ // Determine if the division can be folded into the operands of
+ // its operands.
+ // TODO: Generalize this to non-constants by using known-bits information.
+ const Type *Ty = LHS->getType();
+ unsigned LZ = RHSC->getValue()->getValue().countLeadingZeros();
+ unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ;
+ // For non-power-of-two values, effectively round the value up to the
+ // nearest power of two.
+ if (!RHSC->getValue()->getValue().isPowerOf2())
+ ++MaxShiftAmt;
+ const IntegerType *ExtTy =
+ IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
+ // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
+ if (const SCEVConstant *Step =
+ dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this)))
+ if (!Step->getValue()->getValue()
+ .urem(RHSC->getValue()->getValue()) &&
+ getZeroExtendExpr(AR, ExtTy) ==
+ getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
+ getZeroExtendExpr(Step, ExtTy),
+ AR->getLoop())) {
+ SmallVector<const SCEV *, 4> Operands;
+ for (unsigned i = 0, e = AR->getNumOperands(); i != e; ++i)
+ Operands.push_back(getUDivExpr(AR->getOperand(i), RHS));
+ return getAddRecExpr(Operands, AR->getLoop());
}
+ // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
+ if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
+ SmallVector<const SCEV *, 4> Operands;
+ for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i)
+ Operands.push_back(getZeroExtendExpr(M->getOperand(i), ExtTy));
+ if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
+ // Find an operand that's safely divisible.
+ for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
+ const SCEV *Op = M->getOperand(i);
+ const SCEV *Div = getUDivExpr(Op, RHSC);
+ if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
+ Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
+ M->op_end());
+ Operands[i] = Div;
+ return getMulExpr(Operands);
+ }
+ }
+ }
+ // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
+ if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(LHS)) {
+ SmallVector<const SCEV *, 4> Operands;
+ for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
+ Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
+ if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
+ Operands.clear();
+ for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
+ const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
+ if (isa<SCEVUDivExpr>(Op) ||
+ getMulExpr(Op, RHS) != A->getOperand(i))
+ break;
+ Operands.push_back(Op);
+ }
+ if (Operands.size() == A->getNumOperands())
+ return getAddExpr(Operands);
}
- }
- // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
- if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(LHS)) {
- SmallVector<const SCEV *, 4> Operands;
- for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i)
- Operands.push_back(getZeroExtendExpr(A->getOperand(i), ExtTy));
- if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
- Operands.clear();
- for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
- const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
- if (isa<SCEVUDivExpr>(Op) || getMulExpr(Op, RHS) != A->getOperand(i))
- break;
- Operands.push_back(Op);
- }
- if (Operands.size() == A->getNumOperands())
- return getAddExpr(Operands);
}
- }
- // Fold if both operands are constant.
- if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
- Constant *LHSCV = LHSC->getValue();
- Constant *RHSCV = RHSC->getValue();
- return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
- RHSCV)));
+ // Fold if both operands are constant.
+ if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
+ Constant *LHSCV = LHSC->getValue();
+ Constant *RHSCV = RHSC->getValue();
+ return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
+ RHSCV)));
+ }
}
}
@@ -3319,8 +3323,16 @@
// Turn shift left of a constant amount into a multiply.
if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
+
+ // If the shift count is not less than the bitwidth, the result of
+ // the shift is undefined. Don't try to analyze it, because the
+ // resolution chosen here may differ from the resolution chosen in
+ // other parts of the compiler.
+ if (SA->getValue().uge(BitWidth))
+ break;
+
Constant *X = ConstantInt::get(getContext(),
- APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
+ APInt(BitWidth, 1).shl(SA->getZExtValue()));
return getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X));
}
break;
@@ -3329,8 +3341,16 @@
// Turn logical shift right of a constant into a unsigned divide.
if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
uint32_t BitWidth = cast<IntegerType>(U->getType())->getBitWidth();
+
+ // If the shift count is not less than the bitwidth, the result of
+ // the shift is undefined. Don't try to analyze it, because the
+ // resolution chosen here may differ from the resolution chosen in
+ // other parts of the compiler.
+ if (SA->getValue().uge(BitWidth))
+ break;
+
Constant *X = ConstantInt::get(getContext(),
- APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
+ APInt(BitWidth, 1).shl(SA->getZExtValue()));
return getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
}
break;
@@ -3338,19 +3358,26 @@
case Instruction::AShr:
// For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1)))
- if (Instruction *L = dyn_cast<Instruction>(U->getOperand(0)))
+ if (Operator *L = dyn_cast<Operator>(U->getOperand(0)))
if (L->getOpcode() == Instruction::Shl &&
L->getOperand(1) == U->getOperand(1)) {
- unsigned BitWidth = getTypeSizeInBits(U->getType());
+ uint64_t BitWidth = getTypeSizeInBits(U->getType());
+
+ // If the shift count is not less than the bitwidth, the result of
+ // the shift is undefined. Don't try to analyze it, because the
+ // resolution chosen here may differ from the resolution chosen in
+ // other parts of the compiler.
+ if (CI->getValue().uge(BitWidth))
+ break;
+
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(getContext(), Amt)),
- U->getType());
+ IntegerType::get(getContext(),
+ Amt)),
+ U->getType());
}
break;
Added: llvm/trunk/test/Analysis/ScalarEvolution/undefined.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/undefined.ll?rev=102042&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/undefined.ll (added)
+++ llvm/trunk/test/Analysis/ScalarEvolution/undefined.ll Wed Apr 21 20:35:11 2010
@@ -0,0 +1,39 @@
+; RUN: opt -analyze -scalar-evolution < %s | FileCheck %s
+
+; ScalarEvolution shouldn't attempt to interpret expressions which have
+; undefined results.
+
+define void @foo(i64 %x) {
+
+ %a = udiv i64 %x, 0
+; CHECK: --> (%x /u 0)
+
+ %B = shl i64 %x, 64
+; CHECK: --> %B
+
+ %b = ashr i64 %B, 64
+; CHECK: --> %b
+
+ %c = lshr i64 %x, 64
+; CHECK: --> %c
+
+ %d = shl i64 %x, 64
+; CHECK: --> %d
+
+ %E = shl i64 %x, -1
+; CHECK: --> %E
+
+ %e = ashr i64 %E, -1
+; CHECK: --> %e
+
+ %f = lshr i64 %x, -1
+; CHECK: --> %f
+
+ %g = shl i64 %x, -1
+; CHECK: --> %g
+
+ %h = bitcast i64 undef to i64
+; CHECK: --> undef
+
+ ret void
+}
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