[clang][AArch64] Add validation for Global Register Variable.

[DanielKristofKiss]

Fixes: #76426

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

@llvm/pr-subscribers-clang

Author: Daniel Kiss (DanielKristofKiss)

Changes

Fixes: #76426

---

Full diff: https://github.com/llvm/llvm-project/pull/94271.diff

2 Files Affected:

• (modified) clang/lib/Basic/Targets/AArch64.h (+12)
• (added) clang/test/Driver/aarch64-fixed-register-global.c (+13)

diff --git a/clang/lib/Basic/Targets/AArch64.h b/clang/lib/Basic/Targets/AArch64.h
index 12fb50286f751..9165865029900 100644
--- a/clang/lib/Basic/Targets/AArch64.h
+++ b/clang/lib/Basic/Targets/AArch64.h
@@ -202,6 +202,18 @@ class LLVM_LIBRARY_VISIBILITY AArch64TargetInfo : public TargetInfo {
   bool hasBitIntType() const override { return true; }
 
   bool validateTarget(DiagnosticsEngine &Diags) const override;
+
+  bool validateGlobalRegisterVariable(StringRef RegName, unsigned RegSize,
+                                      bool &HasSizeMismatch) const override {
+    if (RegName.equals("sp") || RegName.starts_with("x")) {
+      HasSizeMismatch = RegSize != 64;
+      return true;
+    } else if (RegName.starts_with("w")) {
+      HasSizeMismatch = RegSize != 32;
+      return true;
+    }
+    return false;
+  }
 };
 
 class LLVM_LIBRARY_VISIBILITY AArch64leTargetInfo : public AArch64TargetInfo {
diff --git a/clang/test/Driver/aarch64-fixed-register-global.c b/clang/test/Driver/aarch64-fixed-register-global.c
new file mode 100644
index 0000000000000..6a05228277cd6
--- /dev/null
+++ b/clang/test/Driver/aarch64-fixed-register-global.c
@@ -0,0 +1,13 @@
+// Check that -ffixed register handled for globals.
+// Regression test for #76426
+// RUN: %clang --target=aarch64-none-gnu -ffixed-x15 -### %s 2>&1 | FileCheck %s
+// CHECK-NOT: fatal error: error in backend: Invalid register name "x15".
+
+register int i1 __asm__("x15");
+
+int foo() {
+  return i1;
+}
+int main() {
+  return foo();
+}

[llvmbot]

@llvm/pr-subscribers-clang-driver

Author: Daniel Kiss (DanielKristofKiss)

Changes

Fixes: #76426

---

Full diff: https://github.com/llvm/llvm-project/pull/94271.diff

2 Files Affected:

• (modified) clang/lib/Basic/Targets/AArch64.h (+12)
• (added) clang/test/Driver/aarch64-fixed-register-global.c (+13)

diff --git a/clang/lib/Basic/Targets/AArch64.h b/clang/lib/Basic/Targets/AArch64.h
index 12fb50286f751..9165865029900 100644
--- a/clang/lib/Basic/Targets/AArch64.h
+++ b/clang/lib/Basic/Targets/AArch64.h
@@ -202,6 +202,18 @@ class LLVM_LIBRARY_VISIBILITY AArch64TargetInfo : public TargetInfo {
   bool hasBitIntType() const override { return true; }
 
   bool validateTarget(DiagnosticsEngine &Diags) const override;
+
+  bool validateGlobalRegisterVariable(StringRef RegName, unsigned RegSize,
+                                      bool &HasSizeMismatch) const override {
+    if (RegName.equals("sp") || RegName.starts_with("x")) {
+      HasSizeMismatch = RegSize != 64;
+      return true;
+    } else if (RegName.starts_with("w")) {
+      HasSizeMismatch = RegSize != 32;
+      return true;
+    }
+    return false;
+  }
 };
 
 class LLVM_LIBRARY_VISIBILITY AArch64leTargetInfo : public AArch64TargetInfo {
diff --git a/clang/test/Driver/aarch64-fixed-register-global.c b/clang/test/Driver/aarch64-fixed-register-global.c
new file mode 100644
index 0000000000000..6a05228277cd6
--- /dev/null
+++ b/clang/test/Driver/aarch64-fixed-register-global.c
@@ -0,0 +1,13 @@
+// Check that -ffixed register handled for globals.
+// Regression test for #76426
+// RUN: %clang --target=aarch64-none-gnu -ffixed-x15 -### %s 2>&1 | FileCheck %s
+// CHECK-NOT: fatal error: error in backend: Invalid register name "x15".
+
+register int i1 __asm__("x15");
+
+int foo() {
+  return i1;
+}
+int main() {
+  return foo();
+}

[kawashima-fj]

@DanielKristofKiss Thanks for the fix. At first glance, LGTM. I'll take a closer look in a few days.
I'm not so familiar with the code. If someone else can review, I'll leave it to them.

[kawashima-fj]

Thanks for the fix. I left a minor suggestion.

Some notes:

• This commit make Clang emit error: size of register '???' does not match variable size error instead of fatal error: error in backend: Invalid register name "???", regardless of the -ffixed-??? option.
• [AArch64] Crash when compiling global register variable __asm__("x15") without -ffixed-x15 #76426 says "When -ffixed-x15 is specified, it can be compiled.". When -ffixed-x15 is specified, older revisions (including 18.1.x releases) compiles the program in [AArch64] Crash when compiling global register variable __asm__("x15") without -ffixed-x15 #76426 without an error but the generated code is incorrect (the foo function is compiled into mrs w0, NZCV; ret!). Recent revisions emits fatal error: error in backend: Invalid register name "x15".. So make it a Clang error is appropriate.
• GCC allows this variable-register size mismatch. Clang does not allow.
• We don't need to use starts_with_insensitive. Register names are case-sensitive (same as GCC).