From: Simon Pilgrim <llvm-dev@redking.me.uk>
Date: Mon, 27 Jun 2016 07:44:32 +0000 (+0000)
Subject: [X86][AVX] Peek through bitcasts to find the source of broadcasts
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=7c1d489b888f2db3f458b30ca138dbc8f67428c1;p=llvm

[X86][AVX] Peek through bitcasts to find the source of broadcasts

AVX1 can only broadcast vectors as floats/doubles, so for 256-bit vectors we insert bitcasts if we are shuffling v8i32/v4i64 types. Unfortunately the presence of these bitcasts prevents the current broadcast lowering code from peeking through cases where we have concatenated / extracted vectors to create the 256-bit vectors.

This patch allows us to peek through bitcasts as long as the number of elements doesn't change (i.e. element bitwidth is the same) so the broadcast index is not affected.

Note this bitcast peek is different from the stage later on which doesn't care about the type and is just trying to find a load node.

Differential Revision: http://reviews.llvm.org/D21660

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273848 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index ebd7fa619f7..8862a194831 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -8510,6 +8510,13 @@ static SDValue lowerVectorShuffleAsBroadcast(const SDLoc &DL, MVT VT,
   SDValue V = V1;
   for (;;) {
     switch (V.getOpcode()) {
+    case ISD::BITCAST: {
+      SDValue VSrc = V.getOperand(0);
+      if (NumElts != VSrc.getSimpleValueType().getVectorNumElements())
+        break;
+      V = VSrc;
+      continue;
+    }
     case ISD::CONCAT_VECTORS: {
       int OperandSize = Mask.size() / V.getNumOperands();
       V = V.getOperand(BroadcastIdx / OperandSize);
diff --git a/test/CodeGen/X86/avx-vbroadcast.ll b/test/CodeGen/X86/avx-vbroadcast.ll
index b7030035444..b312be9aa6b 100644
--- a/test/CodeGen/X86/avx-vbroadcast.ll
+++ b/test/CodeGen/X86/avx-vbroadcast.ll
@@ -173,14 +173,12 @@ define <8 x i32> @load_splat_8i32_4i32_33333333(<4 x i32>* %ptr) nounwind uwtabl
 ; X32-LABEL: load_splat_8i32_4i32_33333333:
 ; X32:       ## BB#0: ## %entry
 ; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X32-NEXT:    vpermilps {{.*#+}} xmm0 = mem[3,3,3,3]
-; X32-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
+; X32-NEXT:    vbroadcastss 12(%eax), %ymm0
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: load_splat_8i32_4i32_33333333:
 ; X64:       ## BB#0: ## %entry
-; X64-NEXT:    vpermilps {{.*#+}} xmm0 = mem[3,3,3,3]
-; X64-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
+; X64-NEXT:    vbroadcastss 12(%rdi), %ymm0
 ; X64-NEXT:    retq
 entry:
   %ld = load <4 x i32>, <4 x i32>* %ptr
@@ -277,16 +275,12 @@ define <4 x i64> @load_splat_4i64_2i64_1111(<2 x i64>* %ptr) nounwind uwtable re
 ; X32-LABEL: load_splat_4i64_2i64_1111:
 ; X32:       ## BB#0: ## %entry
 ; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X32-NEXT:    vmovaps (%eax), %xmm0
-; X32-NEXT:    vmovhlps {{.*#+}} xmm0 = xmm0[1,1]
-; X32-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
+; X32-NEXT:    vbroadcastsd 8(%eax), %ymm0
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: load_splat_4i64_2i64_1111:
 ; X64:       ## BB#0: ## %entry
-; X64-NEXT:    vmovaps (%rdi), %xmm0
-; X64-NEXT:    vmovhlps {{.*#+}} xmm0 = xmm0[1,1]
-; X64-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
+; X64-NEXT:    vbroadcastsd 8(%rdi), %ymm0
 ; X64-NEXT:    retq
 entry:
   %ld = load <2 x i64>, <2 x i64>* %ptr
diff --git a/test/CodeGen/X86/vector-shuffle-256-v4.ll b/test/CodeGen/X86/vector-shuffle-256-v4.ll
index 8c50695b456..610462346fb 100644
--- a/test/CodeGen/X86/vector-shuffle-256-v4.ll
+++ b/test/CodeGen/X86/vector-shuffle-256-v4.ll
@@ -1320,8 +1320,7 @@ define <4 x double> @splat_v4f64(<2 x double> %r) {
 define <4 x i64> @splat_mem_v4i64_from_v2i64(<2 x i64>* %ptr) {
 ; AVX1-LABEL: splat_mem_v4i64_from_v2i64:
 ; AVX1:       # BB#0:
-; AVX1-NEXT:    vmovddup {{.*#+}} xmm0 = mem[0,0]
-; AVX1-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
+; AVX1-NEXT:    vbroadcastsd (%rdi), %ymm0
 ; AVX1-NEXT:    retq
 ;
 ; AVX2-LABEL: splat_mem_v4i64_from_v2i64: