[clang][ARM] Emit an error when an interrupt handler is called.

Closes #95359.

Author: chrisnc

clang/docs/ReleaseNotes.rst

@@ -636,6 +636,8 @@ Improvements to Clang's diagnostics
   used rather than when they are needed for constant evaluation or when code is generated for them.
   The check is now stricter to prevent crashes for some unsupported declarations (Fixes #GH95495).
 
+- For the ARM target, calling an interrupt handler from another function is now an error (#GH95359).
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -340,6 +340,8 @@ def warn_arm_interrupt_vfp_clobber : Warning<
   "interrupt service routine with vfp enabled may clobber the "
   "interruptee's vfp state">,
   InGroup<DiagGroup<"arm-interrupt-vfp-clobber">>;
+def err_arm_interrupt_called : Error<
+  "interrupt service routine cannot be called directly">;
 def warn_interrupt_attribute_invalid : Warning<
    "%select{MIPS|MSP430|RISC-V}0 'interrupt' attribute only applies to "
    "functions that have %select{no parameters|a 'void' return type}1">,

clang/lib/Sema/SemaExpr.cpp

@@ -6765,9 +6765,15 @@ ExprResult Sema::BuildResolvedCallExpr(Expr *Fn, NamedDecl *NDecl,
   unsigned BuiltinID = (FDecl ? FDecl->getBuiltinID() : 0);
 
   // Functions with 'interrupt' attribute cannot be called directly.
-  if (FDecl && FDecl->hasAttr<AnyX86InterruptAttr>()) {
-    Diag(Fn->getExprLoc(), diag::err_anyx86_interrupt_called);
-    return ExprError();
+  if (FDecl) {
+    if (FDecl->hasAttr<AnyX86InterruptAttr>()) {
+      Diag(Fn->getExprLoc(), diag::err_anyx86_interrupt_called);
+      return ExprError();
+    }
+    if (FDecl->hasAttr<ARMInterruptAttr>()) {
+      Diag(Fn->getExprLoc(), diag::err_arm_interrupt_called);
+      return ExprError();
+    }
   }
 
   // X86 interrupt handlers may only call routines with attribute

clang/test/Sema/arm-interrupt-attr.c

@@ -1,8 +1,10 @@
-// RUN: %clang_cc1 %s -triple arm-none-eabi -DSOFT -verify -fsyntax-only
+// RUN: %clang_cc1 %s -triple arm-none-eabi -verify -fsyntax-only
 // RUN: %clang_cc1 %s -triple arm-none-eabi -target-feature +vfp2 -verify -fsyntax-only
 
 
-#ifdef SOFT
+#ifdef __ARM_FP
+__attribute__((interrupt("IRQ"))) void float_irq(void); // expected-warning {{interrupt service routine with vfp enabled may clobber the interruptee's vfp state}}
+#else // !defined(__ARM_FP)
 __attribute__((interrupt("irq"))) void foo1(void) {} // expected-warning {{'interrupt' attribute argument not supported: irq}}
 __attribute__((interrupt(IRQ))) void foo(void) {} // expected-error {{'interrupt' attribute requires a string}}
 __attribute__((interrupt("IRQ", 1))) void foo2(void) {} // expected-error {{'interrupt' attribute takes no more than 1 argument}}
@@ -14,6 +16,11 @@ __attribute__((interrupt("UNDEF"))) void foo7(void) {}
 __attribute__((interrupt)) void foo8(void) {}
 __attribute__((interrupt())) void foo9(void) {}
 __attribute__((interrupt(""))) void foo10(void) {}
-#else
-__attribute__((interrupt("IRQ"))) void float_irq(void); // expected-warning {{interrupt service routine with vfp enabled may clobber the interruptee's vfp state}}
-#endif
+
+__attribute__((interrupt("IRQ"))) void callee(void) {}
+
+void caller(void)
+{
+    callee(); // expected-error {{interrupt service routine cannot be called directly}}
+}
+#endif // __ARM_FP