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-rw-r--r--lib/CodeGen/SelectionDAG/SelectionDAG.cpp20
-rw-r--r--lib/Transforms/Scalar/InstructionCombining.cpp53
-rw-r--r--test/Transforms/InstCombine/add-sitofp.ll9
3 files changed, 31 insertions, 51 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index c46271a2b7..ff505f2c0d 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1628,6 +1628,7 @@ unsigned SelectionDAG::ComputeNumSignBits(SDOperand Op, unsigned Depth) const{
assert(MVT::isInteger(VT) && "Invalid VT!");
unsigned VTBits = MVT::getSizeInBits(VT);
unsigned Tmp, Tmp2;
+ unsigned FirstAnswer = 1;
if (Depth == 6)
return 1; // Limit search depth.
@@ -1683,11 +1684,16 @@ unsigned SelectionDAG::ComputeNumSignBits(SDOperand Op, unsigned Depth) const{
case ISD::AND:
case ISD::OR:
case ISD::XOR: // NOT is handled here.
- // Logical binary ops preserve the number of sign bits.
+ // Logical binary ops preserve the number of sign bits at the worst.
Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1);
- if (Tmp == 1) return 1; // Early out.
- Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1);
- return std::min(Tmp, Tmp2);
+ if (Tmp != 1) {
+ Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1);
+ FirstAnswer = std::min(Tmp, Tmp2);
+ // We computed what we know about the sign bits as our first
+ // answer. Now proceed to the generic code that uses
+ // ComputeMaskedBits, and pick whichever answer is better.
+ }
+ break;
case ISD::SELECT:
Tmp = ComputeNumSignBits(Op.getOperand(1), Depth+1);
@@ -1801,7 +1807,7 @@ unsigned SelectionDAG::ComputeNumSignBits(SDOperand Op, unsigned Depth) const{
Op.getOpcode() == ISD::INTRINSIC_W_CHAIN ||
Op.getOpcode() == ISD::INTRINSIC_VOID) {
unsigned NumBits = TLI.ComputeNumSignBitsForTargetNode(Op, Depth);
- if (NumBits > 1) return NumBits;
+ if (NumBits > 1) FirstAnswer = std::max(FirstAnswer, NumBits);
}
// Finally, if we can prove that the top bits of the result are 0's or 1's,
@@ -1816,7 +1822,7 @@ unsigned SelectionDAG::ComputeNumSignBits(SDOperand Op, unsigned Depth) const{
Mask = KnownOne;
} else {
// Nothing known.
- return 1;
+ return FirstAnswer;
}
// Okay, we know that the sign bit in Mask is set. Use CLZ to determine
@@ -1825,7 +1831,7 @@ unsigned SelectionDAG::ComputeNumSignBits(SDOperand Op, unsigned Depth) const{
Mask <<= Mask.getBitWidth()-VTBits;
// Return # leading zeros. We use 'min' here in case Val was zero before
// shifting. We don't want to return '64' as for an i32 "0".
- return std::min(VTBits, Mask.countLeadingZeros());
+ return std::max(FirstAnswer, std::min(VTBits, Mask.countLeadingZeros()));
}
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 084f874f92..13dbc11526 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2072,6 +2072,7 @@ unsigned InstCombiner::ComputeNumSignBits(Value *V, unsigned Depth) const{
const IntegerType *Ty = cast<IntegerType>(V->getType());
unsigned TyBits = Ty->getBitWidth();
unsigned Tmp, Tmp2;
+ unsigned FirstAnswer = 1;
if (Depth == 6)
return 1; // Limit search depth.
@@ -2101,54 +2102,18 @@ unsigned InstCombiner::ComputeNumSignBits(Value *V, unsigned Depth) const{
}
break;
case Instruction::And:
- // Logical binary ops preserve the number of sign bits at the worst.
- Tmp = ComputeNumSignBits(U->getOperand(0), Depth+1);
- if (Tmp != 1) {
- Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth+1);
- Tmp = std::min(Tmp, Tmp2);
- }
-
- // X & C has sign bits equal to C if C's top bits are zeros.
- if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) {
- // See what bits are known to be zero on the output.
- APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0);
- APInt Mask = APInt::getAllOnesValue(TyBits);
- ComputeMaskedBits(U->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
-
- KnownZero |= ~C->getValue();
- // If we know that we have leading zeros, we know we have at least that
- // many sign bits.
- Tmp = std::max(Tmp, KnownZero.countLeadingOnes());
- }
- return Tmp;
-
case Instruction::Or:
+ case Instruction::Xor: // NOT is handled here.
// Logical binary ops preserve the number of sign bits at the worst.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth+1);
if (Tmp != 1) {
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth+1);
- Tmp = std::min(Tmp, Tmp2);
+ FirstAnswer = std::min(Tmp, Tmp2);
+ // We computed what we know about the sign bits as our first
+ // answer. Now proceed to the generic code that uses
+ // ComputeMaskedBits, and pick whichever answer is better.
}
- // X & C has sign bits equal to C if C's top bits are zeros.
- if (ConstantInt *C = dyn_cast<ConstantInt>(U->getOperand(1))) {
- // See what bits are known to be one on the output.
- APInt KnownZero(TyBits, 0), KnownOne(TyBits, 0);
- APInt Mask = APInt::getAllOnesValue(TyBits);
- ComputeMaskedBits(U->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
-
- KnownOne |= C->getValue();
- // If we know that we have leading ones, we know we have at least that
- // many sign bits.
- Tmp = std::max(Tmp, KnownOne.countLeadingOnes());
- }
- return Tmp;
-
- case Instruction::Xor: // NOT is handled here.
- // Logical binary ops preserve the number of sign bits.
- Tmp = ComputeNumSignBits(U->getOperand(0), Depth+1);
- if (Tmp == 1) return 1; // Early out.
- Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth+1);
- return std::min(Tmp, Tmp2);
+ break;
case Instruction::Select:
Tmp = ComputeNumSignBits(U->getOperand(1), Depth+1);
@@ -2232,7 +2197,7 @@ unsigned InstCombiner::ComputeNumSignBits(Value *V, unsigned Depth) const{
Mask = KnownOne;
} else {
// Nothing known.
- return 1;
+ return FirstAnswer;
}
// Okay, we know that the sign bit in Mask is set. Use CLZ to determine
@@ -2241,7 +2206,7 @@ unsigned InstCombiner::ComputeNumSignBits(Value *V, unsigned Depth) const{
Mask <<= Mask.getBitWidth()-TyBits;
// Return # leading zeros. We use 'min' here in case Val was zero before
// shifting. We don't want to return '64' as for an i32 "0".
- return std::min(TyBits, Mask.countLeadingZeros());
+ return std::max(FirstAnswer, std::min(TyBits, Mask.countLeadingZeros()));
}
diff --git a/test/Transforms/InstCombine/add-sitofp.ll b/test/Transforms/InstCombine/add-sitofp.ll
new file mode 100644
index 0000000000..35c6567da6
--- /dev/null
+++ b/test/Transforms/InstCombine/add-sitofp.ll
@@ -0,0 +1,9 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {add i32}
+
+define double @x(i32 %a, i32 %b) nounwind {
+ %m = lshr i32 %a, 24
+ %n = and i32 %m, %b
+ %o = sitofp i32 %n to double
+ %p = add double %o, 1.0
+ ret double %p
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-18 21:23:50 +0000