[PPCMIPeephole] Fix splat elimination

Summary:
In PPCMIPeephole, when we see two splat instructions, we can't simply do the following transformation:
  B = Splat A
  C = Splat B
=>
  C = Splat A
because B may still be used between these two instructions. Instead, we should make the second Splat a PPC::COPY and let later passes decide whether to remove it or not:
  B = Splat A
  C = Splat B
=>
  B = Splat A
  C = COPY B

Fixes PR30663.

Reviewers: echristo, iteratee, kbarton, nemanjai

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D25493

llvm-svn: 283961

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/PowerPC/pr30663.ll b/llvm/test/CodeGen/PowerPC/pr30663.ll
new file mode 100644
index 00000000000..0772fcaadfe
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/pr30663.ll
@@ -0,0 +1,24 @@
+; RUN: llc -O1 < %s | FileCheck %s
+target triple = "powerpc64le-linux-gnu"
+
+; The second xxspltw should be eliminated.
+; CHECK: xxspltw
+; CHECK-NOT: xxspltw
+define void @Test() {
+bb4:
+  %tmp = load <4 x i8>, <4 x i8>* undef
+  %tmp8 = bitcast <4 x i8> %tmp to float
+  %tmp18 = fmul float %tmp8, undef
+  %tmp19 = fsub float 0.000000e+00, %tmp18
+  store float %tmp19, float* undef
+  %tmp22 = shufflevector <4 x i8> %tmp, <4 x i8> undef, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 0, i32 1, i32 2, i32 3, i32 0, i32 1, i32 2, i32 3, i32 0, i32 1, i32 2, i32 3>
+  %tmp23 = bitcast <16 x i8> %tmp22 to <4 x float>
+  %tmp25 = tail call <4 x float> @llvm.fma.v4f32(<4 x float> undef, <4 x float> %tmp23, <4 x float> undef)
+  %tmp26 = fsub <4 x float> zeroinitializer, %tmp25
+  %tmp27 = bitcast <4 x float> %tmp26 to <4 x i32>
+  tail call void @llvm.ppc.altivec.stvx(<4 x i32> %tmp27, i8* undef)
+  ret void
+}
+
+declare void @llvm.ppc.altivec.stvx(<4 x i32>, i8*)
+declare <4 x float> @llvm.fma.v4f32(<4 x float>, <4 x float>, <4 x float>)