[RISCV] Set __GCC_CONSTRUCTIVE_SIZE/__GCC_DESTRUCTIVE_SIZE to 64 (#162986)

These two macros were added in
#89446.

But the previous values may not be reasonable for RV64 systems because
most
of them have a cache line size 64B. So here we change them to 64.

Author: wangpc-pp

clang/docs/ReleaseNotes.rst

@@ -598,6 +598,9 @@ RISC-V Support
 - Add `-march=unset` to clear any previous `-march=` value. This ISA string will
   be computed from `-mcpu` or the platform default.
 
+- `__GCC_CONSTRUCTIVE_SIZE` and `__GCC_DESTRUCTIVE_SIZE` are changed to 64. These values are
+  unstable according to `Clang's documentation <https://clang.llvm.org/docs/LanguageExtensions.html#gcc-destructive-size-and-gcc-constructive-size>`_.
+
 CUDA/HIP Language Changes
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 

clang/lib/Basic/Targets/RISCV.h

@@ -126,7 +126,7 @@ class RISCVTargetInfo : public TargetInfo {
   llvm::APInt getFMVPriority(ArrayRef<StringRef> Features) const override;
 
   std::pair<unsigned, unsigned> hardwareInterferenceSizes() const override {
-    return std::make_pair(32, 32);
+    return std::make_pair(64, 64);
   }
 
   bool supportsCpuSupports() const override { return getTriple().isOSLinux(); }

clang/test/Preprocessor/init-riscv.c

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -E -dM -triple=riscv32 < /dev/null | \
+// RUN:     FileCheck -match-full-lines -check-prefixes=RV32 %s
+// RUN: %clang_cc1 -E -dM -triple=riscv64 < /dev/null | \
+// RUN:     FileCheck -match-full-lines -check-prefixes=RV64 %s
+
+// RV32: #define __GCC_CONSTRUCTIVE_SIZE 64
+// RV32: #define __GCC_DESTRUCTIVE_SIZE 64
+
+// RV64: #define __GCC_CONSTRUCTIVE_SIZE 64
+// RV64: #define __GCC_DESTRUCTIVE_SIZE 64