[llvm-branch-commits] [llvm] [X86] Remove extra MOV after widening atomic load (PR #138635)

[via llvm-branch-commits]

https://github.com/jofrn updated https://github.com/llvm/llvm-project/pull/138635

>From 6312f8c4dbc5272b5f2c741a46fe7623ace49bf8 Mon Sep 17 00:00:00 2001
From: jofernau_amdeng <joe.fernau at amd.com>
Date: Tue, 6 May 2025 01:48:11 -0400
Subject: [PATCH] [X86] Remove extra MOV after widening atomic load

This change adds patterns to optimize out an extra MOV
present after widening the atomic load.

commit-id:45989503
---
 llvm/lib/Target/X86/X86InstrCompiler.td    |  7 ++++
 llvm/test/CodeGen/X86/atomic-load-store.ll | 40 ++++++++++++----------
 2 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/llvm/lib/Target/X86/X86InstrCompiler.td b/llvm/lib/Target/X86/X86InstrCompiler.td
index efa1e8bd7f3e3..786d0567280f9 100644
--- a/llvm/lib/Target/X86/X86InstrCompiler.td
+++ b/llvm/lib/Target/X86/X86InstrCompiler.td
@@ -1204,6 +1204,13 @@ def : Pat<(i16 (atomic_load_nonext_16 addr:$src)), (MOV16rm addr:$src)>;
 def : Pat<(i32 (atomic_load_nonext_32 addr:$src)), (MOV32rm addr:$src)>;
 def : Pat<(i64 (atomic_load_nonext_64 addr:$src)), (MOV64rm addr:$src)>;
 
+def : Pat<(v4i32 (scalar_to_vector (i32 (zext (i16 (atomic_load_16 addr:$src)))))),
+           (MOVDI2PDIrm addr:$src)>;   // load atomic <2 x i8>
+def : Pat<(v4i32 (scalar_to_vector (i32 (atomic_load_32 addr:$src)))),
+           (MOVDI2PDIrm addr:$src)>;   // load atomic <2 x i16>
+def : Pat<(v2i64 (scalar_to_vector (i64 (atomic_load_64 addr:$src)))),
+           (MOV64toPQIrm  addr:$src)>; // load atomic <2 x i32,float>
+
 // Floating point loads/stores.
 def : Pat<(atomic_store_32 (i32 (bitconvert (f32 FR32:$src))), addr:$dst),
           (MOVSSmr addr:$dst, FR32:$src)>, Requires<[UseSSE1]>;
diff --git a/llvm/test/CodeGen/X86/atomic-load-store.ll b/llvm/test/CodeGen/X86/atomic-load-store.ll
index 9ee8b4fc5ac7f..3cf9e3c1a8dfa 100644
--- a/llvm/test/CodeGen/X86/atomic-load-store.ll
+++ b/llvm/test/CodeGen/X86/atomic-load-store.ll
@@ -165,11 +165,15 @@ define <2 x i8> @atomic_vec2_i8(ptr %x) {
 }
 
 define <2 x i16> @atomic_vec2_i16(ptr %x) {
-; CHECK-LABEL: atomic_vec2_i16:
-; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movl (%rdi), %eax
-; CHECK-NEXT:    movd %eax, %xmm0
-; CHECK-NEXT:    retq
+; CHECK3-LABEL: atomic_vec2_i16:
+; CHECK3:       ## %bb.0:
+; CHECK3-NEXT:    movss {{.*#+}} xmm0 = mem[0],zero,zero,zero
+; CHECK3-NEXT:    retq
+;
+; CHECK0-LABEL: atomic_vec2_i16:
+; CHECK0:       ## %bb.0:
+; CHECK0-NEXT:    movd {{.*#+}} xmm0 = mem[0],zero,zero,zero
+; CHECK0-NEXT:    retq
   %ret = load atomic <2 x i16>, ptr %x acquire, align 4
   ret <2 x i16> %ret
 }
@@ -177,8 +181,7 @@ define <2 x i16> @atomic_vec2_i16(ptr %x) {
 define <2 x ptr addrspace(270)> @atomic_vec2_ptr270(ptr %x) {
 ; CHECK-LABEL: atomic_vec2_ptr270:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movq (%rdi), %rax
-; CHECK-NEXT:    movq %rax, %xmm0
+; CHECK-NEXT:    movq (%rdi), %xmm0
 ; CHECK-NEXT:    retq
   %ret = load atomic <2 x ptr addrspace(270)>, ptr %x acquire, align 8
   ret <2 x ptr addrspace(270)> %ret
@@ -187,8 +190,7 @@ define <2 x ptr addrspace(270)> @atomic_vec2_ptr270(ptr %x) {
 define <2 x i32> @atomic_vec2_i32_align(ptr %x) {
 ; CHECK-LABEL: atomic_vec2_i32_align:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movq (%rdi), %rax
-; CHECK-NEXT:    movq %rax, %xmm0
+; CHECK-NEXT:    movq (%rdi), %xmm0
 ; CHECK-NEXT:    retq
   %ret = load atomic <2 x i32>, ptr %x acquire, align 8
   ret <2 x i32> %ret
@@ -197,8 +199,7 @@ define <2 x i32> @atomic_vec2_i32_align(ptr %x) {
 define <2 x float> @atomic_vec2_float_align(ptr %x) {
 ; CHECK-LABEL: atomic_vec2_float_align:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movq (%rdi), %rax
-; CHECK-NEXT:    movq %rax, %xmm0
+; CHECK-NEXT:    movq (%rdi), %xmm0
 ; CHECK-NEXT:    retq
   %ret = load atomic <2 x float>, ptr %x acquire, align 8
   ret <2 x float> %ret
@@ -354,11 +355,15 @@ define <2 x i32> @atomic_vec2_i32(ptr %x) nounwind {
 }
 
 define <4 x i8> @atomic_vec4_i8(ptr %x) nounwind {
-; CHECK-LABEL: atomic_vec4_i8:
-; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movl (%rdi), %eax
-; CHECK-NEXT:    movd %eax, %xmm0
-; CHECK-NEXT:    retq
+; CHECK3-LABEL: atomic_vec4_i8:
+; CHECK3:       ## %bb.0:
+; CHECK3-NEXT:    movss {{.*#+}} xmm0 = mem[0],zero,zero,zero
+; CHECK3-NEXT:    retq
+;
+; CHECK0-LABEL: atomic_vec4_i8:
+; CHECK0:       ## %bb.0:
+; CHECK0-NEXT:    movd {{.*#+}} xmm0 = mem[0],zero,zero,zero
+; CHECK0-NEXT:    retq
   %ret = load atomic <4 x i8>, ptr %x acquire, align 4
   ret <4 x i8> %ret
 }
@@ -366,8 +371,7 @@ define <4 x i8> @atomic_vec4_i8(ptr %x) nounwind {
 define <4 x i16> @atomic_vec4_i16(ptr %x) nounwind {
 ; CHECK-LABEL: atomic_vec4_i16:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movq (%rdi), %rax
-; CHECK-NEXT:    movq %rax, %xmm0
+; CHECK-NEXT:    movq (%rdi), %xmm0
 ; CHECK-NEXT:    retq
   %ret = load atomic <4 x i16>, ptr %x acquire, align 8
   ret <4 x i16> %ret