[llvm] [X86] combineConcatVectorOps - add handling for FADD/FMUl etc. with a repeated vector op (PR #172682)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon created https://github.com/llvm/llvm-project/pull/172682

Similar to what we already do for integer binops - concatenate the repeated operand instead of the results

>From 1d85dfd5038ed992602e9e4c54c34a7369a9efec Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Wed, 17 Dec 2025 15:44:44 +0000
Subject: [PATCH] [X86] combineConcatVectorOps - add handling for FADD/FMUl
 etc. with a repeated vector op

Similar to what we already do for integer binops - concatenate the repeated operand instead of the results
---
 llvm/lib/Target/X86/X86ISelLowering.cpp |  4 ++-
 llvm/test/CodeGen/X86/combine-fmul.ll   | 46 ++++++++++++-------------
 2 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index aec11ad97ab5c..82cde9c6127fa 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -59662,7 +59662,9 @@ static SDValue combineConcatVectorOps(const SDLoc &DL, MVT VT,
                        (VT.is512BitVector() && Subtarget.useAVX512Regs()))) {
         SDValue Concat0 = CombineSubOperand(VT, Ops, 0);
         SDValue Concat1 = CombineSubOperand(VT, Ops, 1);
-        if (Concat0 || Concat1)
+        if (Concat0 || Concat1 || llvm::all_of(Ops, [](SDValue Op) {
+              return Op.getOperand(0) == Op.getOperand(1);
+            }))
           return DAG.getNode(Opcode, DL, VT,
                              Concat0 ? Concat0 : ConcatSubOperand(VT, Ops, 0),
                              Concat1 ? Concat1 : ConcatSubOperand(VT, Ops, 1));
diff --git a/llvm/test/CodeGen/X86/combine-fmul.ll b/llvm/test/CodeGen/X86/combine-fmul.ll
index 258f782897716..c5966a81147e9 100644
--- a/llvm/test/CodeGen/X86/combine-fmul.ll
+++ b/llvm/test/CodeGen/X86/combine-fmul.ll
@@ -13,9 +13,9 @@ define <4 x double> @concat_fmul_self_v4f64_v2f64(<2 x double> %a0, <2 x double>
 ;
 ; AVX-LABEL: concat_fmul_self_v4f64_v2f64:
 ; AVX:       # %bb.0:
-; AVX-NEXT:    vmulpd %xmm0, %xmm0, %xmm0
-; AVX-NEXT:    vmulpd %xmm1, %xmm1, %xmm1
+; AVX-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
 ; AVX-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; AVX-NEXT:    vmulpd %ymm0, %ymm0, %ymm0
 ; AVX-NEXT:    retq
   %v0 = fmul <2 x double> %a0, %a0
   %v1 = fmul <2 x double> %a1, %a1
@@ -32,9 +32,9 @@ define <8 x float> @concat_fmul_self_v8f32_v4f32(<4 x float> %a0, <4 x float> %a
 ;
 ; AVX-LABEL: concat_fmul_self_v8f32_v4f32:
 ; AVX:       # %bb.0:
-; AVX-NEXT:    vmulps %xmm0, %xmm0, %xmm0
-; AVX-NEXT:    vmulps %xmm1, %xmm1, %xmm1
+; AVX-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
 ; AVX-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; AVX-NEXT:    vmulps %ymm0, %ymm0, %ymm0
 ; AVX-NEXT:    retq
   %v0 = fmul <4 x float> %a0, %a0
   %v1 = fmul <4 x float> %a1, %a1
@@ -53,23 +53,22 @@ define <8 x double> @concat_fmul_self_v8f64_v2f64(<2 x double> %a0, <2 x double>
 ;
 ; AVX1OR2-LABEL: concat_fmul_self_v8f64_v2f64:
 ; AVX1OR2:       # %bb.0:
-; AVX1OR2-NEXT:    vmulpd %xmm0, %xmm0, %xmm0
-; AVX1OR2-NEXT:    vmulpd %xmm1, %xmm1, %xmm1
-; AVX1OR2-NEXT:    vmulpd %xmm2, %xmm2, %xmm2
-; AVX1OR2-NEXT:    vmulpd %xmm3, %xmm3, %xmm3
+; AVX1OR2-NEXT:    # kill: def $xmm2 killed $xmm2 def $ymm2
+; AVX1OR2-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
 ; AVX1OR2-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; AVX1OR2-NEXT:    vmulpd %ymm0, %ymm0, %ymm0
 ; AVX1OR2-NEXT:    vinsertf128 $1, %xmm3, %ymm2, %ymm1
+; AVX1OR2-NEXT:    vmulpd %ymm1, %ymm1, %ymm1
 ; AVX1OR2-NEXT:    retq
 ;
 ; AVX512-LABEL: concat_fmul_self_v8f64_v2f64:
 ; AVX512:       # %bb.0:
-; AVX512-NEXT:    vmulpd %xmm0, %xmm0, %xmm0
-; AVX512-NEXT:    vmulpd %xmm1, %xmm1, %xmm1
-; AVX512-NEXT:    vmulpd %xmm2, %xmm2, %xmm2
-; AVX512-NEXT:    vmulpd %xmm3, %xmm3, %xmm3
+; AVX512-NEXT:    # kill: def $xmm2 killed $xmm2 def $ymm2
+; AVX512-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
 ; AVX512-NEXT:    vinsertf128 $1, %xmm3, %ymm2, %ymm2
 ; AVX512-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
 ; AVX512-NEXT:    vinsertf64x4 $1, %ymm2, %zmm0, %zmm0
+; AVX512-NEXT:    vmulpd %zmm0, %zmm0, %zmm0
 ; AVX512-NEXT:    retq
   %v0 = fmul <2 x double> %a0, %a0
   %v1 = fmul <2 x double> %a1, %a1
@@ -92,23 +91,22 @@ define <16 x float> @concat_fmul_self_v16f32_v4f32(<4 x float> %a0, <4 x float>
 ;
 ; AVX1OR2-LABEL: concat_fmul_self_v16f32_v4f32:
 ; AVX1OR2:       # %bb.0:
-; AVX1OR2-NEXT:    vmulps %xmm0, %xmm0, %xmm0
-; AVX1OR2-NEXT:    vmulps %xmm1, %xmm1, %xmm1
-; AVX1OR2-NEXT:    vmulps %xmm2, %xmm2, %xmm2
-; AVX1OR2-NEXT:    vmulps %xmm3, %xmm3, %xmm3
+; AVX1OR2-NEXT:    # kill: def $xmm2 killed $xmm2 def $ymm2
+; AVX1OR2-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
 ; AVX1OR2-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; AVX1OR2-NEXT:    vmulps %ymm0, %ymm0, %ymm0
 ; AVX1OR2-NEXT:    vinsertf128 $1, %xmm3, %ymm2, %ymm1
+; AVX1OR2-NEXT:    vmulps %ymm1, %ymm1, %ymm1
 ; AVX1OR2-NEXT:    retq
 ;
 ; AVX512-LABEL: concat_fmul_self_v16f32_v4f32:
 ; AVX512:       # %bb.0:
-; AVX512-NEXT:    vmulps %xmm0, %xmm0, %xmm0
-; AVX512-NEXT:    vmulps %xmm1, %xmm1, %xmm1
-; AVX512-NEXT:    vmulps %xmm2, %xmm2, %xmm2
-; AVX512-NEXT:    vmulps %xmm3, %xmm3, %xmm3
+; AVX512-NEXT:    # kill: def $xmm2 killed $xmm2 def $ymm2
+; AVX512-NEXT:    # kill: def $xmm0 killed $xmm0 def $ymm0
 ; AVX512-NEXT:    vinsertf128 $1, %xmm3, %ymm2, %ymm2
 ; AVX512-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
 ; AVX512-NEXT:    vinsertf64x4 $1, %ymm2, %zmm0, %zmm0
+; AVX512-NEXT:    vmulps %zmm0, %zmm0, %zmm0
 ; AVX512-NEXT:    retq
   %v0 = fmul <4 x float> %a0, %a0
   %v1 = fmul <4 x float> %a1, %a1
@@ -137,9 +135,9 @@ define <8 x double> @concat_fmul_self_v8f64_v4f64(<4 x double> %a0, <4 x double>
 ;
 ; AVX512-LABEL: concat_fmul_self_v8f64_v4f64:
 ; AVX512:       # %bb.0:
-; AVX512-NEXT:    vmulpd %ymm0, %ymm0, %ymm0
-; AVX512-NEXT:    vmulpd %ymm1, %ymm1, %ymm1
+; AVX512-NEXT:    # kill: def $ymm0 killed $ymm0 def $zmm0
 ; AVX512-NEXT:    vinsertf64x4 $1, %ymm1, %zmm0, %zmm0
+; AVX512-NEXT:    vmulpd %zmm0, %zmm0, %zmm0
 ; AVX512-NEXT:    retq
   %v0 = fmul <4 x double> %a0, %a0
   %v1 = fmul <4 x double> %a1, %a1
@@ -164,9 +162,9 @@ define <16 x float> @concat_fmul_self_v16f32_v8f32(<8 x float> %a0, <8 x float>
 ;
 ; AVX512-LABEL: concat_fmul_self_v16f32_v8f32:
 ; AVX512:       # %bb.0:
-; AVX512-NEXT:    vmulps %ymm0, %ymm0, %ymm0
-; AVX512-NEXT:    vmulps %ymm1, %ymm1, %ymm1
+; AVX512-NEXT:    # kill: def $ymm0 killed $ymm0 def $zmm0
 ; AVX512-NEXT:    vinsertf64x4 $1, %ymm1, %zmm0, %zmm0
+; AVX512-NEXT:    vmulps %zmm0, %zmm0, %zmm0
 ; AVX512-NEXT:    retq
   %v0 = fmul <8 x float> %a0, %a0
   %v1 = fmul <8 x float> %a1, %a1