[MSP430] Allow msp430_intrcc functions to not have interrupt attribute. (#37)

Summary:
Useful in case you want to have control over interrupt vector generation.
For example in Rust language we have an arrangement where all unhandled
ISR vectors gets mapped to a single default handler function. Which is
hard to implement when LLVM tries to generate vectors on its own.

Reviewers: asl, krisb

Subscribers: hiraditya, JDevlieghere, awygle, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67313

llvm-svn: 372910

Co-authored-by: Vadzim Dambrouski <pftbest@gmail.com>

Author: 2 people

llvm/lib/Target/MSP430/MSP430AsmPrinter.cpp

@@ -159,8 +159,9 @@ void MSP430AsmPrinter::EmitInstruction(const MachineInstr *MI) {
 void MSP430AsmPrinter::EmitInterruptVectorSection(MachineFunction &ISR) {
   MCSection *Cur = OutStreamer->getCurrentSectionOnly();
   const auto *F = &ISR.getFunction();
-  assert(F->hasFnAttribute("interrupt") &&
-         "Functions with MSP430_INTR CC should have 'interrupt' attribute");
+  if (F->getCallingConv() != CallingConv::MSP430_INTR) {
+    report_fatal_error("Functions with 'interrupt' attribute must have msp430_intrcc CC");
+  }
   StringRef IVIdx = F->getFnAttribute("interrupt").getValueAsString();
   MCSection *IV = OutStreamer->getContext().getELFSection(
     "__interrupt_vector_" + IVIdx,
@@ -174,8 +175,9 @@ void MSP430AsmPrinter::EmitInterruptVectorSection(MachineFunction &ISR) {
 
 bool MSP430AsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   // Emit separate section for an interrupt vector if ISR
-  if (MF.getFunction().getCallingConv() == CallingConv::MSP430_INTR)
+  if (MF.getFunction().hasFnAttribute("interrupt")) {
     EmitInterruptVectorSection(MF);
+  }
 
   SetupMachineFunction(MF);
   EmitFunctionBody();

llvm/test/CodeGen/MSP430/interrupt.ll

@@ -50,4 +50,13 @@ entry:
   ret void
 }
 
+; Functions without 'interrupt' attribute don't get a vector section.
+; CHECK-NOT: __interrupt_vector
+; CHECK-LABEL: NMI:
+; CHECK: reti
+define msp430_intrcc void @NMI() #1 {
+  ret void
+}
+
 attributes #0 = { noinline nounwind optnone "interrupt"="2" }
+attributes #1 = { noinline nounwind optnone }