From 02a1141e5a36928f7a0ac9d2e0ee44dca3be3a01 Mon Sep 17 00:00:00 2001 From: Michael Gottesman Date: Tue, 16 Oct 2012 21:29:38 +0000 Subject: [PATCH] [InstCombine] Teach InstCombine how to handle an obfuscated splat. An obfuscated splat is where the frontend poorly generates code for a splat using several different shuffles to create the splat, i.e., %A = load <4 x float>* %in_ptr, align 16 %B = shufflevector <4 x float> %A, <4 x float> undef, <4 x i32> %C = shufflevector <4 x float> %B, <4 x float> %A, <4 x i32> %D = shufflevector <4 x float> %C, <4 x float> %A, <4 x i32> llvm-svn: 166061 --- llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp | 7 +++++-- llvm/test/Transforms/InstCombine/obfuscated_splat.ll | 11 +++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-) create mode 100644 llvm/test/Transforms/InstCombine/obfuscated_splat.ll diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp index cf60f0f4..dd7ea14 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp @@ -636,8 +636,11 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { // If LHS's width is changed, shift the mask value accordingly. // If newRHS == NULL, i.e. LHSOp0 == RHSOp0, we want to remap any - // references to RHSOp0 to LHSOp0, so we don't need to shift the mask. - if (eltMask >= 0 && newRHS != NULL) + // references from RHSOp0 to LHSOp0, so we don't need to shift the mask. + // If newRHS == newLHS, we want to remap any references from newRHS to + // newLHS so that we can properly identify splats that may occur due to + // obfuscation accross the two vectors. + if (eltMask >= 0 && newRHS != NULL && newLHS != newRHS) eltMask += newLHSWidth; } diff --git a/llvm/test/Transforms/InstCombine/obfuscated_splat.ll b/llvm/test/Transforms/InstCombine/obfuscated_splat.ll new file mode 100644 index 0000000..c25dade --- /dev/null +++ b/llvm/test/Transforms/InstCombine/obfuscated_splat.ll @@ -0,0 +1,11 @@ +; RUN: opt -instcombine -S %s | FileCheck %s + +define void @test(<4 x float> *%in_ptr, <4 x float> *%out_ptr) { + %A = load <4 x float>* %in_ptr, align 16 + %B = shufflevector <4 x float> %A, <4 x float> undef, <4 x i32> + %C = shufflevector <4 x float> %B, <4 x float> %A, <4 x i32> + %D = shufflevector <4 x float> %C, <4 x float> %A, <4 x i32> +; CHECK: %D = shufflevector <4 x float> %A, <4 x float> undef, <4 x i32> zeroinitializer + store <4 x float> %D, <4 x float> *%out_ptr + ret void +} -- 2.7.4