[llvm] [RISCV] Fix internal compiler about Zcmp. (PR #66073)

[via llvm-commits]

llvmbot wrote:

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

<details>
<summary>Changes</summary>

The original code encounters ICE when we need to spill callee saves but none of them is GPR.
--
Full diff: https://github.com/llvm/llvm-project/pull/66073.diff

2 Files Affected:

- (modified) llvm/lib/Target/RISCV/RISCVFrameLowering.cpp (+5-5) 
- (added) llvm/test/CodeGen/RISCV/zcmp-crash.ll (+21) 


<pre>
diff --git a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
index add933250f8473d..898412ff446b075 100644
--- a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -1371,12 +1371,12 @@ bool RISCVFrameLowering::spillCalleeSavedRegisters(
   RISCVMachineFunctionInfo *RVFI = MF->getInfo<RISCVMachineFunctionInfo>();
   if (RVFI->isPushable(*MF)) {
     Register MaxReg = getMaxPushPopReg(*MF, CSI);
-    unsigned PushedRegNum =
-        getPushPopEncoding(MaxReg) - llvm::RISCVZC::RLISTENCODE::RA + 1;
-    RVFI->setRVPushRegs(PushedRegNum);
-    RVFI->setRVPushStackSize(alignTo((STI.getXLen() / 8) * PushedRegNum, 16));
-
     if (MaxReg != RISCV::NoRegister) {
+      unsigned PushedRegNum =
+          getPushPopEncoding(MaxReg) - llvm::RISCVZC::RLISTENCODE::RA + 1;
+      RVFI->setRVPushRegs(PushedRegNum);
+      RVFI->setRVPushStackSize(alignTo((STI.getXLen() / 8) * PushedRegNum, 16));
+
       // Use encoded number to represent registers to spill.
       unsigned RegEnc = getPushPopEncoding(MaxReg);
       RVFI->setRVPushRlist(RegEnc);
diff --git a/llvm/test/CodeGen/RISCV/zcmp-crash.ll b/llvm/test/CodeGen/RISCV/zcmp-crash.ll
new file mode 100644
index 000000000000000..b22085f95a3d1b0
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/zcmp-crash.ll
@@ -0,0 +1,21 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
+; RUN: llc -mtriple=riscv32 -target-abi ilp32f -mattr=+f,+zcmp -verify-machineinstrs < %s | FileCheck %s
+
+; Test the file could be compiled successfully.
+define void @bar() {
+; CHECK-LABEL: bar:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    addi sp, sp, -16
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    fsw fs0, 12(sp) # 4-byte Folded Spill
+; CHECK-NEXT:    .cfi_offset fs0, -4
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    fmv.w.x fs0, zero
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    flw fs0, 12(sp) # 4-byte Folded Reload
+; CHECK-NEXT:    addi sp, sp, 16
+; CHECK-NEXT:    ret
+entry:
+  tail call void asm sideeffect "fmv.w.x fs0, zero", "~{fs0}"()
+  ret void
+}
</pre>

</details>

https://github.com/llvm/llvm-project/pull/66073