[clang] Clang/MIPS: Add +fp64 if MSA and no explicit -mfp option (PR #91949)

[YunQiang Su via cfe-commits]

https://github.com/wzssyqa created https://github.com/llvm/llvm-project/pull/91949

MSA requires -mfp64. If FP64 is supported by CPU (mips32r2+), and no -mfp32/-mfpxx is explicitly given, let's add +fp64. Otherwise some cmd like
   clang --target=mips -mips32r5 -mmsa
will issue LLVM backend ICE.

>From effc1a239718ebc20ac835e59223c78d3fd9a01c Mon Sep 17 00:00:00 2001
From: YunQiang Su <syq at gcc.gnu.org>
Date: Mon, 13 May 2024 19:28:25 +0800
Subject: [PATCH] Clang/MIPS: Add +fp64 if MSA and no explicit -mfp option

MSA requires -mfp64. If FP64 is supported by CPU (mips32r2+),
and no -mfp32/-mfpxx is explicitly given, let's add +fp64.
Otherwise some cmd like
   clang --target=mips -mips32r5 -mmsa
will issue LLVM backend ICE.
---
 clang/lib/Driver/ToolChains/Arch/Mips.cpp | 10 ++++++++++
 clang/test/Driver/mips-features.c         |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/Arch/Mips.cpp b/clang/lib/Driver/ToolChains/Arch/Mips.cpp
index 74a8874a3ea2b..79a00711e6f53 100644
--- a/clang/lib/Driver/ToolChains/Arch/Mips.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/Mips.cpp
@@ -369,6 +369,9 @@ void mips::getMIPSTargetFeatures(const Driver &D, const llvm::Triple &Triple,
   } else if (mips::isFP64ADefault(Triple, CPUName)) {
     Features.push_back("+fp64");
     Features.push_back("+nooddspreg");
+  } else if (Arg *A = Args.getLastArg(options::OPT_mmsa)) {
+    if (A->getOption().matches(options::OPT_mmsa))
+      Features.push_back("+fp64");
   }
 
   AddTargetFeature(Args, Features, options::OPT_mno_odd_spreg,
@@ -499,6 +502,13 @@ bool mips::shouldUseFPXX(const ArgList &Args, const llvm::Triple &Triple,
                                options::OPT_mdouble_float))
     if (A->getOption().matches(options::OPT_msingle_float))
       UseFPXX = false;
+  // FP64 should be used for MSA.
+  if (Arg *A = Args.getLastArg(options::OPT_mmsa))
+    if (A->getOption().matches(options::OPT_mmsa))
+      UseFPXX = llvm::StringSwitch<bool>(CPUName)
+                    .Cases("mips32r2", "mips32r3", "mips32r5", false)
+                    .Cases("mips64r2", "mips64r3", "mips64r5", false)
+                    .Default(UseFPXX);
 
   return UseFPXX;
 }
diff --git a/clang/test/Driver/mips-features.c b/clang/test/Driver/mips-features.c
index 5e92dccaa02ab..8b8db4c4a341b 100644
--- a/clang/test/Driver/mips-features.c
+++ b/clang/test/Driver/mips-features.c
@@ -163,6 +163,12 @@
 // RUN:   | FileCheck --check-prefix=CHECK-NOMMSA %s
 // CHECK-NOMMSA: "-target-feature" "-msa"
 //
+// -mmsa
+// RUN: %clang -target mips-linux-gnu -### -c %s \
+// RUN:     -mmsa 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MMSA-MFP64 %s
+// CHECK-MMSA-MFP64: "-target-feature" "+msa" "-target-feature" "+fp64"
+//
 // -mmt
 // RUN: %clang -target mips-linux-gnu -### -c %s \
 // RUN:     -mno-mt -mmt 2>&1 \