[RISCV] Support -m[no-]strict-align options

To match GCC. Options `-m[no-]strict-align` are aliases of `-m[no-]unaligned-access` in clang, but there is no corresponding option in GCC. Support of `-m[no-]unaligned-access` in GCC may be needed to align Clang/GCC. Reviewed By: kito-cheng Differential Revision: https://reviews.llvm.org/D155456
llvm · Aug 3, 2023 · 23ce536 · 23ce536
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diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -171,6 +171,8 @@ LoongArch Support
 
 RISC-V Support
 ^^^^^^^^^^^^^^
+- Unaligned memory accesses can be toggled by ``-m[no-]unaligned-access`` or the
+  aliases ``-m[no-]strict-align``.
 
 CUDA/HIP Language Changes
 ^^^^^^^^^^^^^^^^^^^^^^^^^

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
@@ -3834,9 +3834,9 @@ def mrvv_vector_bits_EQ : Joined<["-"], "mrvv-vector-bits=">, Group<m_Group>,
            "in __riscv_v_fixed_vlen preprocessor define (RISC-V only)">;
 
 def munaligned_access : Flag<["-"], "munaligned-access">, Group<m_Group>,
-  HelpText<"Allow memory accesses to be unaligned (AArch32/AArch64/LoongArch only)">;
+  HelpText<"Allow memory accesses to be unaligned (AArch32/AArch64/LoongArch/RISC-V only)">;
 def mno_unaligned_access : Flag<["-"], "mno-unaligned-access">, Group<m_Group>,
-  HelpText<"Force all memory accesses to be aligned (AArch32/AArch64/LoongArch only)">;
+  HelpText<"Force all memory accesses to be aligned (AArch32/AArch64/LoongArch/RISC-V only)">;
 } // let Flags = [TargetSpecific]
 def mstrict_align : Flag<["-"], "mstrict-align">, Alias<mno_unaligned_access>, Flags<[CC1Option,HelpHidden]>,
   HelpText<"Force all memory accesses to be aligned (same as mno-unaligned-access)">;

diff --git a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
@@ -167,6 +167,19 @@ void riscv::getRISCVTargetFeatures(const Driver &D, const llvm::Triple &Triple,
   else
     Features.push_back("-save-restore");
 
+  // -mno-unaligned-access is default, unless -munaligned-access is specified.
+  bool HasV = llvm::is_contained(Features, "+zve32x");
+  if (Args.hasFlag(options::OPT_munaligned_access,
+                   options::OPT_mno_unaligned_access, false)) {
+    Features.push_back("+unaligned-scalar-mem");
+    if (HasV)
+      Features.push_back("+unaligned-vector-mem");
+  } else {
+    Features.push_back("-unaligned-scalar-mem");
+    if (HasV)
+      Features.push_back("-unaligned-vector-mem");
+  }
+
   // Now add any that the user explicitly requested on the command line,
   // which may override the defaults.
   handleTargetFeaturesGroup(D, Triple, Args, Features,

diff --git a/clang/test/Driver/riscv-default-features.c b/clang/test/Driver/riscv-default-features.c
@@ -3,8 +3,10 @@
 
 // RV32: "target-features"="+32bit,+a,+c,+m,+relax,
 // RV32-SAME: -save-restore
+// RV32-SAME: -unaligned-scalar-mem
 // RV64: "target-features"="+64bit,+a,+c,+m,+relax,
 // RV64-SAME: -save-restore
+// RV64-SAME: -unaligned-scalar-mem
 
 // Dummy function
 int foo(void){

diff --git a/clang/test/Driver/riscv-features.c b/clang/test/Driver/riscv-features.c
@@ -26,6 +26,22 @@
 // DEFAULT: "-target-feature" "-save-restore"
 // DEFAULT-NOT: "-target-feature" "+save-restore"
 
+// RUN: %clang --target=riscv32-unknown-elf -### %s -munaligned-access 2>&1 | FileCheck %s -check-prefix=UNALIGNED-SCALAR-MEM
+// RUN: %clang --target=riscv32-unknown-elf -### %s -mno-unaligned-access 2>&1 | FileCheck %s -check-prefix=NO-UNALIGNED-SCALAR-MEM
+// RUN: %clang --target=riscv32-unknown-elf -### %s -mno-strict-align 2>&1 | FileCheck %s -check-prefix=UNALIGNED-SCALAR-MEM
+// RUN: %clang --target=riscv32-unknown-elf -### %s -mstrict-align 2>&1 | FileCheck %s -check-prefix=NO-UNALIGNED-SCALAR-MEM
+// RUN: %clang --target=riscv32-unknown-elf -### %s -march=rv32gv -munaligned-access 2>&1 | FileCheck %s -check-prefix=UNALIGNED-VECTOR-MEM
+// RUN: %clang --target=riscv32-unknown-elf -### %s -march=rv32gv -mno-unaligned-access 2>&1 | FileCheck %s -check-prefix=NO-UNALIGNED-VECTOR-MEM
+// RUN: %clang --target=riscv32-unknown-elf -### %s -march=rv32gv -mno-strict-align 2>&1 | FileCheck %s -check-prefix=UNALIGNED-VECTOR-MEM
+// RUN: %clang --target=riscv32-unknown-elf -### %s -march=rv32gv -mstrict-align 2>&1 | FileCheck %s -check-prefix=NO-UNALIGNED-VECTOR-MEM
+
+// UNALIGNED-SCALAR-MEM: "-target-feature" "+unaligned-scalar-mem"
+// NO-UNALIGNED-SCALAR-MEM: "-target-feature" "-unaligned-scalar-mem"
+// UNALIGNED-VECTOR-MEM: "-target-feature" "+unaligned-vector-mem"
+// NO-UNALIGNED-VECTOR-MEM: "-target-feature" "-unaligned-vector-mem"
+// DEFAULT: "-target-feature" "-unaligned-scalar-mem"
+// DEFAULT-NOT: "-target-feature" "+unaligned-scalar-mem"
+
 // RUN: %clang --target=riscv32-linux -### %s -fsyntax-only 2>&1 \
 // RUN:   | FileCheck %s -check-prefix=DEFAULT-LINUX
 // RUN: %clang --target=riscv64-linux -### %s -fsyntax-only 2>&1 \