From a68096c73e2200ddf57a9d48bd0ed4d55464e841 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Fri, 2 Nov 2018 15:51:47 +0000 Subject: [ValueTracking] allow non-canonical shuffles when computing signbits This possibility is noted in D53987 for a different case, so we need to adjust the existing code. llvm-svn: 345988 --- llvm/lib/Analysis/ValueTracking.cpp | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'llvm/lib/Analysis/ValueTracking.cpp') diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 3cef373f324..89a621576ec 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -2511,27 +2511,29 @@ static unsigned ComputeNumSignBitsImpl(const Value *V, unsigned Depth, // 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(U)->getMask()->containsUndefElement()) break; - assert((!isa(U->getOperand(0)) || - !isa(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(Op0) && isa(Op1)) + break; // Look through shuffle of 1 source vector. - if (isa(U->getOperand(0))) - return ComputeNumSignBits(U->getOperand(1), Depth + 1, Q); - if (isa(U->getOperand(1))) - return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q); + if (isa(Op0)) + return ComputeNumSignBits(Op1, Depth + 1, Q); + if (isa(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. -- cgit v1.2.3