[RISCV] Fix collectNonISAExtFeature returning negative extension features

[lukel97]

collectNonISAExtFeature was returning any negative extension features, e.g.
given an input of

+zifencei,+m,+a,+save-restore,-zbb,-relax,-zfa

It would return

+save-restore,-zbb,-relax,-zfa

Because negative extensions aren't emitted when calling toFeatureVector(), and
so were considered missing. Hence why we still see "-zfa" and "-zfb" in the tests for
the full arch string attributes, even though with a full arch string we should be overriding the extensions.

This fixes it by using RISCVISAInfo::isSupportedExtensionFeature instead to
check if a feature is an ISA extension.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-backend-risc-v

Author: Luke Lau (lukel97)

Changes

collectNonISAExtFeature was returning any negative extension features, e.g.
given an input of

+zifencei,+m,+a,+save-restore,-zbb,-relax,-zfa

It would return

+save-restore,-zbb,-relax,-zfa

Because negative extensions aren't emitted when calling toFeatureVector(), and
so were considered missing. This is why we see an extra "-zfa" and "-zfb" in the tests for
the full arch string attributes, even when they are both already present in the
command line flags.

This fixes it by using RISCVISAInfo::isSupportedExtensionFeature instead to
check if a feature is an ISA extension.

---

Full diff: https://github.com/llvm/llvm-project/pull/76962.diff

2 Files Affected:

• (modified) clang/lib/Basic/Targets/RISCV.cpp (+6-13)
• (modified) clang/test/CodeGen/RISCV/riscv-func-attr-target.c (+4-4)

diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index 6bc57a83a2d5ae..b98cd093bc9b0e 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -237,22 +237,15 @@ ArrayRef<Builtin::Info> RISCVTargetInfo::getTargetBuiltins() const {
 
 static std::vector<std::string>
 collectNonISAExtFeature(ArrayRef<std::string> FeaturesNeedOverride, int XLen) {
-  auto ParseResult =
-      llvm::RISCVISAInfo::parseFeatures(XLen, FeaturesNeedOverride);
-
-  if (!ParseResult) {
-    consumeError(ParseResult.takeError());
-    return std::vector<std::string>();
-  }
-
-  std::vector<std::string> ImpliedFeatures = (*ParseResult)->toFeatureVector();
-
   std::vector<std::string> NonISAExtFeatureVec;
 
+  auto IsNonISAExtFeature = [](const std::string &Feature) {
+    assert(Feature.size() > 1 && (Feature[0] == '+' || Feature[0] == '-'));
+    std::string Ext = Feature.substr(1); // drop the +/-
+    return !llvm::RISCVISAInfo::isSupportedExtensionFeature(Ext);
+  };
   llvm::copy_if(FeaturesNeedOverride, std::back_inserter(NonISAExtFeatureVec),
-                [&](const std::string &Feat) {
-                  return !llvm::is_contained(ImpliedFeatures, Feat);
-                });
+                IsNonISAExtFeature);
 
   return NonISAExtFeatureVec;
 }
diff --git a/clang/test/CodeGen/RISCV/riscv-func-attr-target.c b/clang/test/CodeGen/RISCV/riscv-func-attr-target.c
index 506acaba687417..759c33a2250600 100644
--- a/clang/test/CodeGen/RISCV/riscv-func-attr-target.c
+++ b/clang/test/CodeGen/RISCV/riscv-func-attr-target.c
@@ -40,8 +40,8 @@ __attribute__((target("cpu=sifive-u54"))) void testAttrCpuOnly() {}
 // CHECK: attributes #1 = { {{.*}}"target-cpu"="rocket-rv64" "target-features"="+64bit,+a,+d,+f,+m,+save-restore,+v,+zicsr,+zifencei,+zve32f,+zve32x,+zve64d,+zve64f,+zve64x,+zvl128b,+zvl32b,+zvl64b,-relax,-zbb,-zfa" "tune-cpu"="generic-rv64" }
 // CHECK: attributes #2 = { {{.*}}"target-features"="+64bit,+a,+m,+save-restore,+zbb,+zifencei,-relax,-zfa" }
 // CHECK: attributes #3 = { {{.*}}"target-features"="+64bit,+a,+d,+experimental-zicond,+f,+m,+save-restore,+v,+zbb,+zicsr,+zifencei,+zve32f,+zve32x,+zve64d,+zve64f,+zve64x,+zvl128b,+zvl32b,+zvl64b,-relax,-zfa" }
-// CHECK: attributes #4 = { {{.*}}"target-features"="+64bit,+a,+c,+d,+f,+m,+save-restore,+zbb,+zicsr,+zifencei,-relax,-zfa" }
-// CHECK: attributes #5 = { {{.*}}"target-features"="+64bit,+m,+save-restore,-relax,-zbb,-zfa" }
+// CHECK: attributes #4 = { {{.*}}"target-features"="+64bit,+a,+c,+d,+f,+m,+save-restore,+zbb,+zicsr,+zifencei,-relax" }
+// CHECK: attributes #5 = { {{.*}}"target-features"="+64bit,+m,+save-restore,-relax" }
 // CHECK: attributes #6 = { {{.*}}"target-cpu"="sifive-u54" "target-features"="+64bit,+a,+m,+save-restore,+zbb,+zifencei,-relax,-zfa" }
-// CHECK: attributes #7 = { {{.*}}"target-cpu"="sifive-u54" "target-features"="+64bit,+m,+save-restore,-relax,-zbb,-zfa" }
-// CHECK: attributes #8 = { {{.*}}"target-cpu"="sifive-u54" "target-features"="+64bit,+a,+c,+d,+f,+m,+save-restore,+zicsr,+zifencei,-relax,-zbb,-zfa" }
+// CHECK: attributes #7 = { {{.*}}"target-cpu"="sifive-u54" "target-features"="+64bit,+m,+save-restore,-relax" }
+// CHECK: attributes #8 = { {{.*}}"target-cpu"="sifive-u54" "target-features"="+64bit,+a,+c,+d,+f,+m,+save-restore,+zicsr,+zifencei,-relax" }

[lukel97]

Note that this doesn't fix the issue described in #74889 (review). One approach that would build upon this would be to use the entire list of target features including negative extensions when a full arch string is specified.