https://github.com/statham-arm created
https://github.com/llvm/llvm-project/pull/149538
The Armv8-M architecture doesn't have the LDREXD and STREXD instructions, for
exclusive load/store of a 64-bit quantity split across two registers. But the
`__ARM_FEATURE_LDREX` macro was set to a value that claims it does, because the
case for Armv8 was missing a check for M profile.
The Armv7 case got it right, so I've just made the two cases the same.
>From 9eb51f1ca408747f82ab07adad5bbcc06e323d23 Mon Sep 17 00:00:00 2001
From: Simon Tatham <simon.tat...@arm.com>
Date: Thu, 17 Jul 2025 16:33:33 +0100
Subject: [PATCH] [Clang][ARM] Fix __ARM_FEATURE_LDREX on Armv8-M
The Armv8-M architecture doesn't have the LDREXD and STREXD
instructions, for exclusive load/store of a 64-bit quantity split
across two registers. But the `__ARM_FEATURE_LDREX` macro was set to
a value that claims it does, because the case for Armv8 was missing a
check for M profile.
The Armv7 case got it right, so I've just made the two cases the same.
---
clang/lib/Basic/Targets/ARM.cpp | 4 +++-
clang/test/Preprocessor/arm-acle-6.4.c | 31 ++++++++++++++++++++++++++
2 files changed, 34 insertions(+), 1 deletion(-)
diff --git a/clang/lib/Basic/Targets/ARM.cpp b/clang/lib/Basic/Targets/ARM.cpp
index 7ff8e51f8a7f8..29de34bbc4fe4 100644
--- a/clang/lib/Basic/Targets/ARM.cpp
+++ b/clang/lib/Basic/Targets/ARM.cpp
@@ -623,13 +623,15 @@ bool
ARMTargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
LDREX = LDREX_W;
break;
case 7:
+ case 8:
if (ArchProfile == llvm::ARM::ProfileKind::M)
LDREX = LDREX_W | LDREX_H | LDREX_B;
else
LDREX = LDREX_D | LDREX_W | LDREX_H | LDREX_B;
break;
- case 8:
case 9:
+ assert(ArchProfile != llvm::ARM::ProfileKind::M &&
+ "No Armv9-M architectures defined");
LDREX = LDREX_D | LDREX_W | LDREX_H | LDREX_B;
}
diff --git a/clang/test/Preprocessor/arm-acle-6.4.c
b/clang/test/Preprocessor/arm-acle-6.4.c
index 2c8f4868263a6..48deba74c8ab2 100644
--- a/clang/test/Preprocessor/arm-acle-6.4.c
+++ b/clang/test/Preprocessor/arm-acle-6.4.c
@@ -188,6 +188,37 @@
// RUN: %clang --target=arm-arm-none-eabi -mcpu=cortex-m33 -x c -E -dM %s -o -
| FileCheck %s -check-prefix CHECK-M-DSP
// RUN: %clang --target=arm-arm-none-eabi -march=armv8m.main+dsp -x c -E -dM
%s -o - | FileCheck %s -check-prefix CHECK-M-DSP
+// RUN: %clang -target arm-none-linux-eabi -march=armv8m.base -x c -E -dM %s
-o - | FileCheck %s -check-prefix CHECK-V8M-BASE
+
+// CHECK-V8M-BASE-NOT: __ARM_ARCH_ISA_ARM
+// CHECK-V8M-BASE-NOT: __ARM_FEATURE_DSP
+// CHECK-V8M-BASE-NOT: __ARM_FEATURE_SIMD32
+// CHECK-V8M-BASE: __ARM_ARCH 8
+// CHECK-V8M-BASE: __ARM_ARCH_ISA_THUMB 1
+// CHECK-V8M-BASE: __ARM_ARCH_PROFILE 'M'
+// CHECK-V8M-BASE: __ARM_FEATURE_CLZ 1
+// CHECK-V8M-BASE: __ARM_FEATURE_IDIV 1
+// CHECK-V8M-BASE: __ARM_FEATURE_LDREX 0x7
+// CHECK-V8M-BASE: __ARM_FEATURE_QBIT 1
+// CHECK-V8M-BASE: __ARM_FEATURE_SAT
+// CHECK-V8M-BASE-NOT: __ARM_FEATURE_UNALIGNED
+
+// RUN: %clang -target arm-none-linux-eabi -march=armv8m.main -x c -E -dM %s
-o - | FileCheck %s -check-prefix CHECK-V8M-MAIN
+// RUN: %clang -target arm-none-linux-eabi -march=armv8.1m.main -x c -E -dM %s
-o - | FileCheck %s -check-prefix CHECK-V8M-MAIN
+
+// CHECK-V8M-MAIN-NOT: __ARM_ARCH_ISA_ARM
+// CHECK-V8M-MAIN-NOT: __ARM_FEATURE_DSP
+// CHECK-V8M-MAIN-NOT: __ARM_FEATURE_SIMD32
+// CHECK-V8M-MAIN: __ARM_ARCH 8
+// CHECK-V8M-MAIN: __ARM_ARCH_ISA_THUMB 2
+// CHECK-V8M-MAIN: __ARM_ARCH_PROFILE 'M'
+// CHECK-V8M-MAIN: __ARM_FEATURE_CLZ 1
+// CHECK-V8M-MAIN: __ARM_FEATURE_IDIV 1
+// CHECK-V8M-MAIN: __ARM_FEATURE_LDREX 0x7
+// CHECK-V8M-MAIN: __ARM_FEATURE_QBIT 1
+// CHECK-V8M-MAIN: __ARM_FEATURE_SAT 1
+// CHECK-V8M-MAIN: __ARM_FEATURE_UNALIGNED 1
+
// CHECK-M-DSP: __ARM_FEATURE_DSP 1
// CHECK-M-DSP: __ARM_FEATURE_SIMD32 1
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