search for: d70246

Sanjay, I'm looking at some missed optimizations caused by D70246. Here's a test case: define <4 x float> @f(i32 %t32, <4 x float>* %t24) { .entry: %t43 = insertelement <3 x i32> undef, i32 %t32, i32 2 %t44 = bitcast <3 x i32> %t43 to <3 x float> %t45 = shufflevector <3 x float> %t44, <3 x float> undef, <4 x...

...o mean exactly what it says. This would imply it's forbidden to transform the shuffle mask "<2 x i32> <i32 undef, i32 0>" to "<2 x i32> <i32 1, i32 0>" if the input might contain poison. (And this is the same logic that led to https://reviews.llvm.org/D70246 .) That said, long-term, we probably want to switch shufflevector to produce poison. -Eli > -----Original Message----- > From: Nuno Lopes <nuno.lopes at ist.utl.pt> > Sent: Tuesday, November 26, 2019 3:20 PM > To: LLVMdev <llvm-dev at lists.llvm.org> > Cc: spatel at ro...

Hi, This is a follow up on a discussion around shufflevector with undef mask in https://reviews.llvm.org/D70641 and https://bugs.llvm.org/show_bug.cgi?id=43958. The current semantics of shufflevector in http://llvm.org/docs/LangRef.html#shufflevector-instruction states: "If the shuffle mask is undef, the result vector is undef. If any element of the mask operand is undef, that element

...o mean exactly what it says. This would imply it's forbidden to transform the shuffle mask "<2 x i32> <i32 undef, i32 0>" to "<2 x i32> <i32 1, i32 0>" if the input might contain poison. (And this is the same logic that led to https://reviews.llvm.org/D70246 .) That said, long-term, we probably want to switch shufflevector to produce poison. -Eli -----Original Message----- From: Nuno Lopes <nuno.lopes at ist.utl.pt><mailto:nuno.lopes at ist.utl.pt> Sent: Tuesday, November 26, 2019 3:20 PM To: LLVMdev <llvm-dev at lists.llvm.org>&...