[llvm] [WebAssembly] Fold offsets into extending SIMD loads (PR #219144)
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Thu Aug 27 01:40:55 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-webassembly
Author: Anutosh Bhat (anutosh491)
<details>
<summary>Changes</summary>
I saw this TODO and realized that instead of lowering to
```
local.get 0
i32.const 8
i32.add
v128.load64_zero 0
f64x2.promote_low_f32x4
```
We could choose
```
local.get 0
v128.load64_zero 8
f64x2.promote_low_f32x4
```
So I used the existing WebAssembly address operand patterns when lowering v2f32-to-v2f64 extending loads.
This allows constant address offsets to be folded into `v128.load64_zero`, avoiding a separate constant and add instruction. The existing no-offset case continues to work with an offset of zero.
---
Full diff: https://github.com/llvm/llvm-project/pull/219144.diff
2 Files Affected:
- (modified) llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td (+8-6)
- (modified) llvm/test/CodeGen/WebAssembly/simd-load-promote-wide.ll (+15-29)
``````````diff
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
index 3e9783a9d1f25..823bf14d03202 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -1667,13 +1667,15 @@ defm "" : HalfPrecisionConvert<F32x4, I16x8, promote_low, "promote_low_f16x8",
def extloadv2f32 : PatFrag<(ops node:$ptr), (extload node:$ptr)> {
let MemoryVT = v2f32;
}
-// Adapted from the body of LoadPatNoOffset
-// TODO: other addressing patterns
-def : Pat<(v2f64 (extloadv2f32 (i32 I32:$addr))),
- (promote_low_F64x2 (LOAD_ZERO_64_A32 0, 0, I32:$addr))>,
+def : Pat<(v2f64 (extloadv2f32
+ (AddrOps32 offset32_op:$offset, I32:$addr))),
+ (promote_low_F64x2
+ (LOAD_ZERO_64_A32 0, offset32_op:$offset, I32:$addr))>,
Requires<[HasAddr32]>;
-def : Pat<(v2f64 (extloadv2f32 (i64 I64:$addr))),
- (promote_low_F64x2 (LOAD_ZERO_64_A64 0, 0, I64:$addr))>,
+def : Pat<(v2f64 (extloadv2f32
+ (AddrOps64 offset64_op:$offset, I64:$addr))),
+ (promote_low_F64x2
+ (LOAD_ZERO_64_A64 0, offset64_op:$offset, I64:$addr))>,
Requires<[HasAddr64]>;
//===----------------------------------------------------------------------===//
diff --git a/llvm/test/CodeGen/WebAssembly/simd-load-promote-wide.ll b/llvm/test/CodeGen/WebAssembly/simd-load-promote-wide.ll
index 0000470f3e2a1..7282dc84f9ab3 100644
--- a/llvm/test/CodeGen/WebAssembly/simd-load-promote-wide.ll
+++ b/llvm/test/CodeGen/WebAssembly/simd-load-promote-wide.ll
@@ -12,9 +12,7 @@ define <4 x double> @load_promote_v2f64(ptr %p) {
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
-; CHECK-NEXT: i32.const 8
-; CHECK-NEXT: i32.add
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: v128.load64_zero 8
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 16
; CHECK-NEXT: local.get 0
@@ -34,16 +32,12 @@ define <4 x double> @load_promote_v2f64_with_folded_offset(ptr %p) {
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
-; CHECK-NEXT: i32.const 24
-; CHECK-NEXT: i32.add
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: v128.load64_zero 24
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 16
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
-; CHECK-NEXT: i32.const 16
-; CHECK-NEXT: i32.add
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: v128.load64_zero 16
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 0
; CHECK-NEXT: # fallthrough-return
@@ -61,16 +55,12 @@ define <4 x double> @load_promote_v2f64_with_folded_gep_offset(ptr %p) {
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
-; CHECK-NEXT: i32.const 24
-; CHECK-NEXT: i32.add
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: v128.load64_zero 24
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 16
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
-; CHECK-NEXT: i32.const 16
-; CHECK-NEXT: i32.add
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: v128.load64_zero 16
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 0
; CHECK-NEXT: # fallthrough-return
@@ -89,16 +79,14 @@ define <4 x double> @load_promote_v2f64_with_unfolded_gep_negative_offset(ptr %p
; CHECK-NEXT: i32.const -16
; CHECK-NEXT: i32.add
; CHECK-NEXT: local.tee 1
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: v128.load64_zero 8
; CHECK-NEXT: f64x2.promote_low_f32x4
-; CHECK-NEXT: v128.store 0
+; CHECK-NEXT: v128.store 16
; CHECK-NEXT: local.get 0
; CHECK-NEXT: local.get 1
-; CHECK-NEXT: i32.const 8
-; CHECK-NEXT: i32.add
; CHECK-NEXT: v128.load64_zero 0
; CHECK-NEXT: f64x2.promote_low_f32x4
-; CHECK-NEXT: v128.store 16
+; CHECK-NEXT: v128.store 0
; CHECK-NEXT: # fallthrough-return
%s = getelementptr inbounds <4 x float>, ptr %p, i32 -1
%e = load <4 x float>, ptr %s
@@ -163,13 +151,13 @@ define <4 x double> @load_promote_v2f64_from_numeric_address() {
; CHECK: .functype load_promote_v2f64_from_numeric_address (i32) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
-; CHECK-NEXT: i32.const 40
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: i32.const 0
+; CHECK-NEXT: v128.load64_zero 40
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 16
; CHECK-NEXT: local.get 0
-; CHECK-NEXT: i32.const 32
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: i32.const 0
+; CHECK-NEXT: v128.load64_zero 32
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 0
; CHECK-NEXT: # fallthrough-return
@@ -185,15 +173,13 @@ define <4 x double> @load_promote_v2f64_from_global_address() {
; CHECK: .functype load_promote_v2f64_from_global_address (i32) -> ()
; CHECK-NEXT: # %bb.0:
; CHECK-NEXT: local.get 0
-; CHECK-NEXT: i32.const gv_v4f32
; CHECK-NEXT: i32.const 8
-; CHECK-NEXT: i32.add
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: v128.load64_zero gv_v4f32
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 16
; CHECK-NEXT: local.get 0
-; CHECK-NEXT: i32.const gv_v4f32
-; CHECK-NEXT: v128.load64_zero 0
+; CHECK-NEXT: i32.const 0
+; CHECK-NEXT: v128.load64_zero gv_v4f32
; CHECK-NEXT: f64x2.promote_low_f32x4
; CHECK-NEXT: v128.store 0
; CHECK-NEXT: # fallthrough-return
``````````
</details>
https://github.com/llvm/llvm-project/pull/219144
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