// extended, shifted, etc).
return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
- case Instruction::ShuffleVector:
+ case Instruction::ShuffleVector: {
// If the shuffle mask contains any undefined elements, that element of the
// result is undefined. Propagating information from a source operand may
// not be correct in that case, so just bail out.
if (cast<ShuffleVectorInst>(U)->getMask()->containsUndefElement())
break;
- assert((!isa<UndefValue>(U->getOperand(0)) ||
- !isa<UndefValue>(U->getOperand(1)))
- && "Should have simplified shuffle with 2 undef inputs");
+ // If everything is undef, we can't say anything. This should be simplified.
+ Value *Op0 = U->getOperand(0), *Op1 = U->getOperand(1);
+ if (isa<UndefValue>(Op0) && isa<UndefValue>(Op1))
+ break;
// Look through shuffle of 1 source vector.
- if (isa<UndefValue>(U->getOperand(0)))
- return ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
- if (isa<UndefValue>(U->getOperand(1)))
- return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
+ if (isa<UndefValue>(Op0))
+ return ComputeNumSignBits(Op1, Depth + 1, Q);
+ if (isa<UndefValue>(Op1))
+ return ComputeNumSignBits(Op0, Depth + 1, Q);
// TODO: We can look through shuffles of 2 sources by computing the minimum
// sign bits for each operand (similar to what we do for binops).
break;
}
+ }
// Finally, if we can prove that the top bits of the result are 0's or 1's,
// use this information.
EXPECT_EQ(ComputeNumSignBits(RVal, M->getDataLayout()), 1u);
}
+// No guarantees for canonical IR in this analysis, so this just bails out.
+TEST(ValueTracking, ComputeNumSignBits_Shuffle) {
+ StringRef Assembly = "define <2 x i32> @f() { "
+ " %val = shufflevector <2 x i32> undef, <2 x i32> undef, <2 x i32> <i32 0, i32 0> "
+ " ret <2 x i32> %val "
+ "} ";
+
+ LLVMContext Context;
+ SMDiagnostic Error;
+ auto M = parseAssemblyString(Assembly, Error, Context);
+ assert(M && "Bad assembly?");
+
+ auto *F = M->getFunction("f");
+ assert(F && "Bad assembly?");
+
+ auto *RVal =
+ cast<ReturnInst>(F->getEntryBlock().getTerminator())->getOperand(0);
+ EXPECT_EQ(ComputeNumSignBits(RVal, M->getDataLayout()), 1u);
+}
+
TEST(ValueTracking, ComputeKnownBits) {
StringRef Assembly = "define i32 @f(i32 %a, i32 %b) { "
" %ash = mul i32 %a, 8 "