[llvm] [WebAssembly] Constant fold wasm.dot (PR #149619)
Jasmine Tang via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 22 13:46:42 PDT 2025
https://github.com/badumbatish updated https://github.com/llvm/llvm-project/pull/149619
>From 5563f46b0d4b559e0d29d508a3acbbf270a173c2 Mon Sep 17 00:00:00 2001
From: Jasmine Tang <jjasmine at igalia.com>
Date: Fri, 18 Jul 2025 14:11:05 -0700
Subject: [PATCH 1/3] [WebAssembly] Precommit test for constant folding dot
---
.../InstSimplify/ConstProp/WebAssembly/dot.ll | 37 +++++++++++++++++++
1 file changed, 37 insertions(+)
create mode 100644 llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
new file mode 100644
index 0000000000000..75a500c6278ad
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
@@ -0,0 +1,37 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+
+; RUN: opt -passes=instsimplify -S < %s | FileCheck %s
+
+; Test that intrinsics wasm dot call are constant folded
+
+target triple = "wasm32-unknown-unknown"
+
+
+define <4 x i32> @dot_zero() {
+; CHECK-LABEL: define <4 x i32> @dot_zero() {
+; CHECK-NEXT: [[RES:%.*]] = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> zeroinitializer, <8 x i16> zeroinitializer)
+; CHECK-NEXT: ret <4 x i32> [[RES]]
+;
+ %res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> zeroinitializer, <8 x i16> zeroinitializer)
+ ret <4 x i32> %res
+}
+
+define <4 x i32> @dot_nonzero() {
+; CHECK-LABEL: define <4 x i32> @dot_nonzero() {
+; CHECK-NEXT: [[RES:%.*]] = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>, <8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>)
+; CHECK-NEXT: ret <4 x i32> [[RES]]
+;
+ %res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>, <8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>)
+ ret <4 x i32> %res
+}
+
+define <4 x i32> @dot_doubly_negative() {
+; CHECK-LABEL: define <4 x i32> @dot_doubly_negative() {
+; CHECK-NEXT: [[RES:%.*]] = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> splat (i16 -1), <8 x i16> splat (i16 -1))
+; CHECK-NEXT: ret <4 x i32> [[RES]]
+;
+ %res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1>, <8 x i16> <i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1>)
+ ret <4 x i32> %res
+}
+
+
>From 50ca839dbee8ea3d505dee87c3e21c458ee28b7f Mon Sep 17 00:00:00 2001
From: Jasmine Tang <jjasmine at igalia.com>
Date: Fri, 18 Jul 2025 16:34:41 -0700
Subject: [PATCH 2/3] [WebAssembly] Constant fold dot operation
---
llvm/lib/Analysis/ConstantFolding.cpp | 31 +++++++++++++++++++
.../InstSimplify/ConstProp/WebAssembly/dot.ll | 14 +++++----
2 files changed, 39 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 9c1c2c6e60f02..2304c58b3f95f 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1657,6 +1657,7 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
case Intrinsic::aarch64_sve_convert_from_svbool:
case Intrinsic::wasm_alltrue:
case Intrinsic::wasm_anytrue:
+ case Intrinsic::wasm_dot:
// WebAssembly float semantics are always known
case Intrinsic::wasm_trunc_signed:
case Intrinsic::wasm_trunc_unsigned:
@@ -3826,6 +3827,36 @@ static Constant *ConstantFoldFixedVectorCall(
}
return ConstantVector::get(Result);
}
+ case Intrinsic::wasm_dot: {
+ unsigned NumElements =
+ cast<FixedVectorType>(Operands[0]->getType())->getNumElements();
+
+ assert(NumElements == 8 && NumElements / 2 == Result.size() &&
+ "wasm dot takes i16x8 and produce i32x4");
+ assert(Ty->isIntegerTy());
+ SmallVector<APInt, 8> MulVector;
+
+ for (unsigned I = 0; I < NumElements; ++I) {
+ ConstantInt *Elt0 =
+ cast<ConstantInt>(Operands[0]->getAggregateElement(I));
+ ConstantInt *Elt1 =
+ cast<ConstantInt>(Operands[1]->getAggregateElement(I));
+
+ // sext 32 first, according to specs
+ APInt IMul = Elt0->getValue().sext(32) * Elt1->getValue().sext(32);
+
+ // TODO: imul in specs includes a modulo operation
+ // Is this performed automatically via trunc = true in APInt creation of *
+ MulVector.push_back(IMul);
+ }
+ for (unsigned I = 0; I < Result.size(); ++I) {
+ // Same case as with imul
+ APInt IAdd = MulVector[I] + MulVector[I + Result.size()];
+ Result[I] = ConstantInt::get(Ty, IAdd);
+ }
+
+ return ConstantVector::get(Result);
+ }
default:
break;
}
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
index 75a500c6278ad..02c6649becbce 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
@@ -9,17 +9,20 @@ target triple = "wasm32-unknown-unknown"
define <4 x i32> @dot_zero() {
; CHECK-LABEL: define <4 x i32> @dot_zero() {
-; CHECK-NEXT: [[RES:%.*]] = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> zeroinitializer, <8 x i16> zeroinitializer)
-; CHECK-NEXT: ret <4 x i32> [[RES]]
+; CHECK-NEXT: ret <4 x i32> zeroinitializer
;
%res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> zeroinitializer, <8 x i16> zeroinitializer)
ret <4 x i32> %res
}
+; a = 1 2 3 4 5 6 7 8
+; b = 1 2 3 4 5 6 7 8
+; k1|k2 = a * b = 1 4 9 16 25 36 49 64
+; k1 + k2 = (1+25) | (4+36) | (9+49) | (16+64)
+; result = 26 | 40 | 58 | 80
define <4 x i32> @dot_nonzero() {
; CHECK-LABEL: define <4 x i32> @dot_nonzero() {
-; CHECK-NEXT: [[RES:%.*]] = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>, <8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>)
-; CHECK-NEXT: ret <4 x i32> [[RES]]
+; CHECK-NEXT: ret <4 x i32> <i32 26, i32 40, i32 58, i32 80>
;
%res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>, <8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>)
ret <4 x i32> %res
@@ -27,8 +30,7 @@ define <4 x i32> @dot_nonzero() {
define <4 x i32> @dot_doubly_negative() {
; CHECK-LABEL: define <4 x i32> @dot_doubly_negative() {
-; CHECK-NEXT: [[RES:%.*]] = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> splat (i16 -1), <8 x i16> splat (i16 -1))
-; CHECK-NEXT: ret <4 x i32> [[RES]]
+; CHECK-NEXT: ret <4 x i32> splat (i32 2)
;
%res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1>, <8 x i16> <i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1, i16 -1>)
ret <4 x i32> %res
>From fa8c096313e2eab8661a5d63b04477f01c86ed78 Mon Sep 17 00:00:00 2001
From: Jasmine Tang <jjasmine at igalia.com>
Date: Tue, 22 Jul 2025 13:40:55 -0700
Subject: [PATCH 3/3] Addresses specs questions and added test to reflect
---
llvm/lib/Analysis/ConstantFolding.cpp | 9 ++++-----
.../InstSimplify/ConstProp/WebAssembly/dot.ll | 18 +++++++++++++++---
2 files changed, 19 insertions(+), 8 deletions(-)
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 2304c58b3f95f..a63be47e21eaa 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -3845,13 +3845,12 @@ static Constant *ConstantFoldFixedVectorCall(
// sext 32 first, according to specs
APInt IMul = Elt0->getValue().sext(32) * Elt1->getValue().sext(32);
- // TODO: imul in specs includes a modulo operation
- // Is this performed automatically via trunc = true in APInt creation of *
+ // i16 -> i32 bypasses specs modulo on imul
MulVector.push_back(IMul);
}
- for (unsigned I = 0; I < Result.size(); ++I) {
- // Same case as with imul
- APInt IAdd = MulVector[I] + MulVector[I + Result.size()];
+ for (unsigned I = 0; I < Result.size(); I++) {
+ // i16 -> i32 bypasses specs modulo on iadd
+ APInt IAdd = MulVector[I * 2] + MulVector[I * 2 + 1];
Result[I] = ConstantInt::get(Ty, IAdd);
}
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
index 02c6649becbce..b2f23d0f153ef 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/dot.ll
@@ -18,11 +18,11 @@ define <4 x i32> @dot_zero() {
; a = 1 2 3 4 5 6 7 8
; b = 1 2 3 4 5 6 7 8
; k1|k2 = a * b = 1 4 9 16 25 36 49 64
-; k1 + k2 = (1+25) | (4+36) | (9+49) | (16+64)
-; result = 26 | 40 | 58 | 80
+; k1 + k2 = (1+4) | (9 + 16) | (25 + 36) | (49 + 64)
+; result = 5 | 25 | 61 | 113
define <4 x i32> @dot_nonzero() {
; CHECK-LABEL: define <4 x i32> @dot_nonzero() {
-; CHECK-NEXT: ret <4 x i32> <i32 26, i32 40, i32 58, i32 80>
+; CHECK-NEXT: ret <4 x i32> <i32 5, i32 25, i32 61, i32 113>
;
%res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>, <8 x i16> <i16 1, i16 2, i16 3, i16 4, i16 5, i16 6, i16 7, i16 8>)
ret <4 x i32> %res
@@ -36,4 +36,16 @@ define <4 x i32> @dot_doubly_negative() {
ret <4 x i32> %res
}
+; This test checks for llvm's compliance on spec's wasm.dot's imul and iadd
+; Since the original number can only be i16::max == 2^15 - 1,
+; subsequent modulo of 2^32 of imul and iadd
+; should return the same result
+; 2*(2^15 - 1)^2 % 2^32 == 2*(2^15 - 1)^2
+define <4 x i32> @dot_follow_modulo_spec() {
+; CHECK-LABEL: define <4 x i32> @dot_follow_modulo_spec() {
+; CHECK-NEXT: ret <4 x i32> <i32 2147352578, i32 0, i32 0, i32 0>
+;
+ %res = tail call <4 x i32> @llvm.wasm.dot(<8 x i16> <i16 32767, i16 32767, i16 0, i16 0, i16 0, i16 0, i16 0, i16 0>, <8 x i16> <i16 32767, i16 32767, i16 0, i16 0, i16 0, i16 0, i16 0, i16 0>)
+ ret <4 x i32> %res
+}
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