[clang] b7f5647 - [Clang] Fix incorrect type for `__mfp8` in `extractelement` codegen (#192977)
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Mon May 11 02:45:33 PDT 2026
Author: Momchil Velikov
Date: 2026-05-11T10:45:28+01:00
New Revision: b7f564781acbb6f373bd24752fd6b3977f376723
URL: https://github.com/llvm/llvm-project/commit/b7f564781acbb6f373bd24752fd6b3977f376723
DIFF: https://github.com/llvm/llvm-project/commit/b7f564781acbb6f373bd24752fd6b3977f376723.diff
LOG: [Clang] Fix incorrect type for `__mfp8` in `extractelement` codegen (#192977)
The codegen for extracting an element from an FP8 vector was emitting a
simple `extractelement` with `i8` type for the extracted element. The
`__mfp8` type is represented as `<1 x i8>` in LLVM IR. This codegen
created inconsistency in Clang - some `__mfp8` expressions would
correspond to LLVM IR values with `<1 x i8>` type and some to `i8` type.
It also caused an assertion failure when the extracted element was
passed as a function argument.
This patch fixes the issue by inserting the extracted element
into a `<1 x i8>`.
Added:
clang/test/CodeGen/AArch64/fp8-extract.c
Modified:
clang/lib/CodeGen/CGExprScalar.cpp
clang/test/CodeGen/arm-mfp8.c
Removed:
################################################################################
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index d60f1b37be50e..c8a8ec7b6d928 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -2213,7 +2213,15 @@ Value *ScalarExprEmitter::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
if (CGF.SanOpts.has(SanitizerKind::ArrayBounds))
CGF.EmitBoundsCheck(E, E->getBase(), Idx, IdxTy, /*Accessed*/true);
- return Builder.CreateExtractElement(Base, Idx, "vecext");
+ Value *Ret = Builder.CreateExtractElement(Base, Idx, "vecext");
+
+ // Even being a scalar the `__mfp8` type corresponds to `<1 x i8>` in LLVM IR.
+ if (E->getType()->isMFloat8Type())
+ Ret = Builder.CreateInsertElement(
+ llvm::PoisonValue::get(llvm::FixedVectorType::get(CGF.Int8Ty, 1)), Ret,
+ uint64_t(0), "mfp8ext");
+
+ return Ret;
}
Value *ScalarExprEmitter::VisitMatrixSingleSubscriptExpr(
diff --git a/clang/test/CodeGen/AArch64/fp8-extract.c b/clang/test/CodeGen/AArch64/fp8-extract.c
new file mode 100644
index 0000000000000..7fa93c6f15305
--- /dev/null
+++ b/clang/test/CodeGen/AArch64/fp8-extract.c
@@ -0,0 +1,52 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 6
+// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +neon -disable-O0-optnone -Werror -Wall -emit-llvm -o - %s | opt -S -p mem2reg,instcombine | FileCheck %s
+// RUN: %clang_cc1 -x c++ -triple aarch64-none-linux-gnu -target-feature +neon -disable-O0-optnone -Werror -Wall -emit-llvm -o - %s | opt -S -p mem2reg,instcombine | FileCheck %s -check-prefix CHECK-CXX
+
+// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +neon -disable-O0-optnone -Werror -Wall -S -o /dev/null %s
+
+// REQUIRES: aarch64-registered-target
+
+#include <arm_neon.h>
+
+// Test for a n internal compiler error when extracting an element from an FP8
+// vector and passing it to a function.
+
+// CHECK-LABEL: define dso_local void @test_var(
+// CHECK-SAME: <16 x i8> [[V:%.*]], i32 noundef [[I:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: [[VECEXT:%.*]] = extractelement <16 x i8> [[V]], i32 [[I]]
+// CHECK-NEXT: [[MFP8CAST:%.*]] = insertelement <1 x i8> poison, i8 [[VECEXT]], i64 0
+// CHECK-NEXT: call void @g(<1 x i8> [[MFP8CAST]]) #[[ATTR2:[0-9]+]]
+// CHECK-NEXT: ret void
+//
+// CHECK-CXX-LABEL: define dso_local void @_Z8test_var14__Mfloat8x16_ti(
+// CHECK-CXX-SAME: <16 x i8> [[V:%.*]], i32 noundef [[I:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK-CXX-NEXT: [[ENTRY:.*:]]
+// CHECK-CXX-NEXT: [[VECEXT:%.*]] = extractelement <16 x i8> [[V]], i32 [[I]]
+// CHECK-CXX-NEXT: [[MFP8CAST:%.*]] = insertelement <1 x i8> poison, i8 [[VECEXT]], i64 0
+// CHECK-CXX-NEXT: call void @_Z1gu6__mfp8(<1 x i8> [[MFP8CAST]]) #[[ATTR2:[0-9]+]]
+// CHECK-CXX-NEXT: ret void
+//
+void test_var(__Mfloat8x16_t v, int i) {
+ void g(__mfp8);
+ g(v[i]);
+}
+
+// CHECK-LABEL: define dso_local void @test_cst(
+// CHECK-SAME: <16 x i8> [[V:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: [[MFP8CAST:%.*]] = shufflevector <16 x i8> [[V]], <16 x i8> poison, <1 x i32> <i32 3>
+// CHECK-NEXT: call void @g(<1 x i8> [[MFP8CAST]]) #[[ATTR2]]
+// CHECK-NEXT: ret void
+//
+// CHECK-CXX-LABEL: define dso_local void @_Z8test_cst14__Mfloat8x16_t(
+// CHECK-CXX-SAME: <16 x i8> [[V:%.*]]) #[[ATTR0]] {
+// CHECK-CXX-NEXT: [[ENTRY:.*:]]
+// CHECK-CXX-NEXT: [[MFP8CAST:%.*]] = shufflevector <16 x i8> [[V]], <16 x i8> poison, <1 x i32> <i32 3>
+// CHECK-CXX-NEXT: call void @_Z1gu6__mfp8(<1 x i8> [[MFP8CAST]]) #[[ATTR2]]
+// CHECK-CXX-NEXT: ret void
+//
+void test_cst(__Mfloat8x16_t v) {
+ void g(__mfp8);
+ g(v[3]);
+}
diff --git a/clang/test/CodeGen/arm-mfp8.c b/clang/test/CodeGen/arm-mfp8.c
index 9385b537f18b3..82df375a45686 100644
--- a/clang/test/CodeGen/arm-mfp8.c
+++ b/clang/test/CodeGen/arm-mfp8.c
@@ -64,20 +64,16 @@ __mfp8 func1n(__mfp8 mfp8) {
// CHECK-C-LABEL: define dso_local <1 x i8> @test_extract_element(
// CHECK-C-SAME: <16 x i8> [[X:%.*]], i32 noundef [[I:%.*]]) #[[ATTR0]] {
// CHECK-C-NEXT: [[ENTRY:.*:]]
-// CHECK-C-NEXT: [[RETVAL:%.*]] = alloca <1 x i8>, align 1
// CHECK-C-NEXT: [[VECEXT:%.*]] = extractelement <16 x i8> [[X]], i32 [[I]]
-// CHECK-C-NEXT: store i8 [[VECEXT]], ptr [[RETVAL]], align 1
-// CHECK-C-NEXT: [[TMP0:%.*]] = load <1 x i8>, ptr [[RETVAL]], align 1
-// CHECK-C-NEXT: ret <1 x i8> [[TMP0]]
+// CHECK-C-NEXT: [[MFP8CAST:%.*]] = insertelement <1 x i8> poison, i8 [[VECEXT]], i64 0
+// CHECK-C-NEXT: ret <1 x i8> [[MFP8CAST]]
//
// CHECK-CXX-LABEL: define dso_local <1 x i8> @_Z20test_extract_element14__Mfloat8x16_ti(
// CHECK-CXX-SAME: <16 x i8> [[X:%.*]], i32 noundef [[I:%.*]]) #[[ATTR0]] {
// CHECK-CXX-NEXT: [[ENTRY:.*:]]
-// CHECK-CXX-NEXT: [[RETVAL:%.*]] = alloca <1 x i8>, align 1
// CHECK-CXX-NEXT: [[VECEXT:%.*]] = extractelement <16 x i8> [[X]], i32 [[I]]
-// CHECK-CXX-NEXT: store i8 [[VECEXT]], ptr [[RETVAL]], align 1
-// CHECK-CXX-NEXT: [[TMP0:%.*]] = load <1 x i8>, ptr [[RETVAL]], align 1
-// CHECK-CXX-NEXT: ret <1 x i8> [[TMP0]]
+// CHECK-CXX-NEXT: [[MFP8CAST:%.*]] = insertelement <1 x i8> poison, i8 [[VECEXT]], i64 0
+// CHECK-CXX-NEXT: ret <1 x i8> [[MFP8CAST]]
//
mfloat8_t test_extract_element(mfloat8x16_t x, int i) {
return x[i];
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