[clang] [RISCV] Support predefined marcro __riscv_misaligned_{fast,avoid}. (PR #65756)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

<details>
<summary>Changes</summary>

RISC-V C API introduced predefined macro to achieve hints about unaligned accesses ([pr]). This patch defines __riscv_misaligned_fast when using -mno-strict-align, otherwise, defines __riscv_misaligned_avoid.

Note: This ignores __riscv_misaligned_slow which is also defined by spec.

[pr]: https://github.com/riscv-non-isa/riscv-c-api-doc/pull/40
---
Full diff: https://github.com/llvm/llvm-project/pull/65756.diff


3 Files Affected:

- (modified) clang/lib/Basic/Targets/RISCV.cpp (+7) 
- (modified) clang/lib/Basic/Targets/RISCV.h (+3) 
- (modified) clang/test/Preprocessor/riscv-target-features.c (+12) 


``````````diff
diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index d55ab76395c8271..119d905be57249b 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -204,6 +204,11 @@ void RISCVTargetInfo::getTargetDefines(const LangOptions &Opts,
   if (VScale && VScale->first && VScale->first == VScale->second)
     Builder.defineMacro("__riscv_v_fixed_vlen",
                         Twine(VScale->first * llvm::RISCV::RVVBitsPerBlock));
+
+  if (FastUnalignedAccess)
+    Builder.defineMacro("__riscv_misaligned_fast");
+  else
+    Builder.defineMacro("__riscv_misaligned_avoid");
 }
 
 static constexpr Builtin::Info BuiltinInfo[] = {
@@ -322,6 +327,8 @@ bool RISCVTargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
   if (ISAInfo->hasExtension("zfh") || ISAInfo->hasExtension("zhinx"))
     HasLegalHalfType = true;
 
+  FastUnalignedAccess = llvm::is_contained(Features, "+unaligned-scalar-mem");
+
   return true;
 }
 
diff --git a/clang/lib/Basic/Targets/RISCV.h b/clang/lib/Basic/Targets/RISCV.h
index 6be0e49ca2f5525..e5424d318401fb0 100644
--- a/clang/lib/Basic/Targets/RISCV.h
+++ b/clang/lib/Basic/Targets/RISCV.h
@@ -29,6 +29,9 @@ class RISCVTargetInfo : public TargetInfo {
   std::string ABI, CPU;
   std::unique_ptr<llvm::RISCVISAInfo> ISAInfo;
 
+private:
+  bool FastUnalignedAccess;
+
 public:
   RISCVTargetInfo(const llvm::Triple &Triple, const TargetOptions &)
       : TargetInfo(Triple) {
diff --git a/clang/test/Preprocessor/riscv-target-features.c b/clang/test/Preprocessor/riscv-target-features.c
index 4dd83cfa0620b90..4db1cf7a49272fb 100644
--- a/clang/test/Preprocessor/riscv-target-features.c
+++ b/clang/test/Preprocessor/riscv-target-features.c
@@ -1228,3 +1228,15 @@
 // RUN: -march=rv64i_zve32x_zvkt1p0 -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-ZVKT-EXT %s
 // CHECK-ZVKT-EXT: __riscv_zvkt 1000000{{$}}
+
+// RUN: %clang --target=riscv32-unknown-linux-gnu -march=rv32i -x c -E -dM %s \
+// RUN: -o - | FileCheck %s --check-prefix=CHECK-MISALIGNED-AVOID
+// RUN: %clang --target=riscv64-unknown-linux-gnu -march=rv64i -x c -E -dM %s \
+// RUN: -o - | FileCheck %s --check-prefix=CHECK-MISALIGNED-AVOID
+// CHECK-MISALIGNED-AVOID: __riscv_misaligned_avoid 1
+
+// RUN: %clang --target=riscv32-unknown-linux-gnu -march=rv32i -x c -E -dM %s \
+// RUN: -munaligned-access -o - | FileCheck %s --check-prefix=CHECK-MISALIGNED-FAST
+// RUN: %clang --target=riscv64-unknown-linux-gnu -march=rv64i -x c -E -dM %s \
+// RUN: -munaligned-access -o - | FileCheck %s --check-prefix=CHECK-MISALIGNED-FAST
+// CHECK-MISALIGNED-FAST: __riscv_misaligned_fast 1

``````````

</details>


https://github.com/llvm/llvm-project/pull/65756