[PATCH] D149249: [X86] Handle multiple use freeze(undef) in LowerAVXCONCAT_VECTORS as zero vectors

[Simon Pilgrim via Phabricator via llvm-commits]

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Replacement for D144903 <https://reviews.llvm.org/D144903>

If we're concatenating freeze(undef) subvector ops with multiple uses then we can't treat them as a wider freeze(undef), but we can replace them with a zero subvector, which is cheap on AVX


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149249

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/avx512-intrinsics.ll
  llvm/test/CodeGen/X86/avx512fp16-intrinsics.ll


Index: llvm/test/CodeGen/X86/avx512fp16-intrinsics.ll
===================================================================
--- llvm/test/CodeGen/X86/avx512fp16-intrinsics.ll
+++ llvm/test/CodeGen/X86/avx512fp16-intrinsics.ll
@@ -1231,10 +1231,7 @@
 define <32 x half> @test_mm512_castph128_ph512_freeze(<8 x half> %a0) nounwind {
 ; CHECK-LABEL: test_mm512_castph128_ph512_freeze:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm1
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
-; CHECK-NEXT:    vinsertf64x4 $1, %ymm1, %zmm0, %zmm0
+; CHECK-NEXT:    vmovaps %xmm0, %xmm0
 ; CHECK-NEXT:    retq
   %a1 = freeze <8 x half> poison
   %res = shufflevector <8 x half> %a0, <8 x half> %a1, <32 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
Index: llvm/test/CodeGen/X86/avx512-intrinsics.ll
===================================================================
--- llvm/test/CodeGen/X86/avx512-intrinsics.ll
+++ llvm/test/CodeGen/X86/avx512-intrinsics.ll
@@ -7495,10 +7495,7 @@
 define <8 x double> @test_mm256_castpd128_pd256_freeze(<2 x double> %a0) nounwind {
 ; CHECK-LABEL: test_mm256_castpd128_pd256_freeze:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm1
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
-; CHECK-NEXT:    vinsertf64x4 $1, %ymm1, %zmm0, %zmm0
+; CHECK-NEXT:    vmovaps %xmm0, %xmm0
 ; CHECK-NEXT:    ret{{[l|q]}}
   %a1 = freeze <2 x double> poison
   %res = shufflevector <2 x double> %a0, <2 x double> %a1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 2, i32 3, i32 2, i32 3>
@@ -7520,10 +7517,7 @@
 define <16 x float> @test_mm256_castps128_ps512_freeze(<4 x float> %a0) nounwind {
 ; CHECK-LABEL: test_mm256_castps128_ps512_freeze:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm1
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
-; CHECK-NEXT:    vinsertf64x4 $1, %ymm1, %zmm0, %zmm0
+; CHECK-NEXT:    vmovaps %xmm0, %xmm0
 ; CHECK-NEXT:    ret{{[l|q]}}
   %a1 = freeze <4 x float> poison
   %res = shufflevector <4 x float> %a0, <4 x float> %a1, <16x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 4, i32 5, i32 6, i32 7, i32 4, i32 5, i32 6, i32 7>
@@ -7545,10 +7539,7 @@
 define <8 x i64> @test_mm512_castsi128_si512_freeze(<2 x i64> %a0) nounwind {
 ; CHECK-LABEL: test_mm512_castsi128_si512_freeze:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm1
-; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
-; CHECK-NEXT:    vinsertf64x4 $1, %ymm1, %zmm0, %zmm0
+; CHECK-NEXT:    vmovaps %xmm0, %xmm0
 ; CHECK-NEXT:    ret{{[l|q]}}
   %a1 = freeze <2 x i64> poison
   %res = shufflevector <2 x i64> %a0, <2 x i64> %a1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 2, i32 3, i32 2, i32 3>
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -11663,8 +11663,13 @@
     SDValue SubVec = Op.getOperand(i);
     if (SubVec.isUndef())
       continue;
-    if (ISD::isFreezeUndef(SubVec.getNode()) && SubVec.hasOneUse())
-      ++NumFreezeUndef;
+    if (ISD::isFreezeUndef(SubVec.getNode())) {
+        // If the freeze(undef) has multiple uses then we must fold to zero.
+        if (SubVec.hasOneUse())
+          ++NumFreezeUndef;
+        else
+          ++NumZero;
+    }
     else if (ISD::isBuildVectorAllZeros(SubVec.getNode()))
       ++NumZero;
     else {


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