[RISCV] Don't emit save-restore call if function is a interrupt handler

[Jim]

Summary

It has to save all caller-saved registers before a call in the handler.
So don't emit a call that save/restore registers.

[simoncook]

This LGTM, I've left a note on a potential comment update, but otherwise looks good

llvm/lib/Target/RISCV/RISCVMachineFunctionInfo.h

63

Can you update this comment to put , or is an interrupt handler

[Jim]

Address comment

[luismarques]

Thanks, good catch. LGTM.

I wonder if this test should just go in the existing saverestore.ll test?

[Jim]

Address @luismarques's comment

[jrtc27]

llvm/test/CodeGen/RISCV/saverestore.ll

304 ↗

(On Diff #337689)

Inline the attribute

[Jim]

Address @jrtc27's comment.

llvm/lib/Target/RISCV/RISCVMachineFunctionInfo.h

int getMoveF64FrameIndex(MachineFunction &MF) {
     return MoveF64FrameIndex;
   }
 
   unsigned getLibCallStackSize() const { return LibCallStackSize; }
   void setLibCallStackSize(unsigned Size) { LibCallStackSize = Size; }
 
   bool useSaveRestoreLibCalls(const MachineFunction &MF) const {
     // We cannot use fixed locations for the callee saved spill slots if the
     // function uses a varargs save area.
     return MF.getSubtarget<RISCVSubtarget>().enableSaveRestore() &&
-           VarArgsSaveSize == 0 && !MF.getFrameInfo().hasTailCall();
+           VarArgsSaveSize == 0 && !MF.getFrameInfo().hasTailCall() &&
+           !MF.getFunction().hasFnAttribute("interrupt");
   }
 
   uint64_t getRVVStackSize() const { return RVVStackSize; }
   void setRVVStackSize(uint64_t Size) { RVVStackSize = Size; }
 
   uint64_t getRVVPadding() const { return RVVPadding; }
   void setRVVPadding(uint64_t Padding) { RVVPadding = Padding; }
 
   unsigned getCalleeSavedStackSize() const { return CalleeSavedStackSize; }
   void setCalleeSavedStackSize(unsigned Size) { CalleeSavedStackSize = Size; }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_LIB_TARGET_RISCV_RISCVMACHINEFUNCTIONINFO_H

llvm/test/CodeGen/RISCV/interrupt-attr-save-restore-call.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple riscv32-unknown-elf -mattr=+save-restore -o - %s \
+; RUN: 2>&1 | FileCheck %s -check-prefix CHECK-RV32
+; RUN: llc -mtriple riscv64-unknown-elf -mattr=+save-restore -o - %s \
+; RUN: 2>&1 | FileCheck %s -check-prefix CHECK-RV64
+
+;
+; Checking save-restore calls not emitted for the handler when save-restore is enabled
+;
+
+declare i32 @otherfoo(...)
+define void @foo_with_call() #0 {
+; CHECK-RV32-LABEL: foo_with_call:
+; CHECK-RV32:       # %bb.0:
+; CHECK-RV32-NEXT:    addi sp, sp, -64
+; CHECK-RV32-NEXT:    sw ra, 60(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw t0, 56(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw t1, 52(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw t2, 48(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a0, 44(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a1, 40(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a2, 36(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a3, 32(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a4, 28(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a5, 24(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a6, 20(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw a7, 16(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw t3, 12(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw t4, 8(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw t5, 4(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    sw t6, 0(sp) # 4-byte Folded Spill
+; CHECK-RV32-NEXT:    call otherfoo
+; CHECK-RV32-NEXT:    lw t6, 0(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw t5, 4(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw t4, 8(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw t3, 12(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a7, 16(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a6, 20(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a5, 24(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a4, 28(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a3, 32(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a2, 36(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a1, 40(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw a0, 44(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw t2, 48(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw t1, 52(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw t0, 56(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    lw ra, 60(sp) # 4-byte Folded Reload
+; CHECK-RV32-NEXT:    addi sp, sp, 64
+; CHECK-RV32-NEXT:    uret
+;
+; CHECK-RV64-LABEL: foo_with_call:
+; CHECK-RV64:       # %bb.0:
+; CHECK-RV64-NEXT:    addi sp, sp, -128
+; CHECK-RV64-NEXT:    sd ra, 120(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd t0, 112(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd t1, 104(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd t2, 96(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a0, 88(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a1, 80(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a2, 72(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a3, 64(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a4, 56(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a5, 48(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a6, 40(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd a7, 32(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd t3, 24(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd t4, 16(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd t5, 8(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    sd t6, 0(sp) # 8-byte Folded Spill
+; CHECK-RV64-NEXT:    call otherfoo
+; CHECK-RV64-NEXT:    ld t6, 0(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld t5, 8(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld t4, 16(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld t3, 24(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a7, 32(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a6, 40(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a5, 48(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a4, 56(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a3, 64(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a2, 72(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a1, 80(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld a0, 88(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld t2, 96(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld t1, 104(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld t0, 112(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    ld ra, 120(sp) # 8-byte Folded Reload
+; CHECK-RV64-NEXT:    addi sp, sp, 128
+; CHECK-RV64-NEXT:    uret
+  %call = call i32 bitcast (i32 (...)* @otherfoo to i32 ()*)()
+  ret void
+}
+
+attributes #0 = { nounwind "interrupt"="user" }