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

[Yeting Kuo via cfe-commits]

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

RISC-V C API introduced predefined macro to achieve hints about unaligned accesses [0]. 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.

The spec has mentioned https://github.com/riscv-non-isa/riscv-c-api-doc/pull/40

[0]: https://github.com/riscv-non-isa/riscv-c-api-doc/pull/40

>From 4d5ad30326642ac6dfce478f7726bafbf51b041c Mon Sep 17 00:00:00 2001
From: Yeting Kuo <yeting.kuo at sifive.com>
Date: Fri, 8 Sep 2023 19:46:03 +0800
Subject: [PATCH] [RISCV] Support predefined marcro
 __riscv_misaligned_{fast,avoid}.

RISC-V C API introduce predefined macro to achieve hints about unaligned accesses [0].
This 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.

The spec has mentioned https://github.com/riscv-non-isa/riscv-c-api-doc/pull/40

[0]: https://github.com/riscv-non-isa/riscv-c-api-doc/pull/40
---
 clang/lib/Basic/Targets/RISCV.cpp               |  7 +++++++
 clang/lib/Basic/Targets/RISCV.h                 |  3 +++
 clang/test/Preprocessor/riscv-target-features.c | 12 ++++++++++++
 3 files changed, 22 insertions(+)

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 02b67dc7944ba88..17e281a81e785b3 100644
--- a/clang/test/Preprocessor/riscv-target-features.c
+++ b/clang/test/Preprocessor/riscv-target-features.c
@@ -1220,3 +1220,15 @@
 // 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