[llvm] clang crash assigning to a global named register variable #109778 (PR #113105)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: Akshay Kumar (akshaykumars614)

<details>
<summary>Changes</summary>

fixed crash

I am not sure if the fix is correct. I tried to analyze the logic and found potential issue in the logic and corrected it. Because of this, two testcases;

arm64-named-reg-alloc.ll :
; RUN: not --crash llc < %s -mtriple=arm64-apple-darwin 2>&1 | FileCheck %s
; RUN: not --crash llc < %s -mtriple=arm64-linux-gnueabi 2>&1 | FileCheck %s

define i32 @<!-- -->get_stack() nounwind {
entry:
; FIXME: Include an allocatable-specific error message
; CHECK: Invalid register name "x5".
        %sp = call i32 @<!-- -->llvm.read_register.i32(metadata !0)
  ret i32 %sp
}

declare i32 @<!-- -->llvm.read_register.i32(metadata) nounwind

!0 = !{!"x5\00"}


aarch64-named-reg-x18.ll :
; RUN: llc -mtriple=aarch64-fuchsia -o - %s

define void @<!-- -->set_x18(i64 %x) {
entry:
; FIXME: Include an allocatable-specific error message
  tail call void @<!-- -->llvm.write_register.i64(metadata !0, i64 %x)
  ret void
}

declare void @<!-- -->llvm.write_register.i64(metadata, i64) nounwind

!0 = !{!"x18"}


I am new to project. Please help me here.

---
Full diff: https://github.com/llvm/llvm-project/pull/113105.diff


1 Files Affected:

- (modified) llvm/lib/Target/AArch64/AArch64ISelLowering.cpp (+2-2) 


``````````diff
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 7448416c682abc..98703d8368813a 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -11522,8 +11522,8 @@ getRegisterByName(const char* RegName, LLT VT, const MachineFunction &MF) const
   if (AArch64::X1 <= Reg && Reg <= AArch64::X28) {
     const AArch64RegisterInfo *MRI = Subtarget->getRegisterInfo();
     unsigned DwarfRegNum = MRI->getDwarfRegNum(Reg, false);
-    if (!Subtarget->isXRegisterReserved(DwarfRegNum) &&
-        !MRI->isReservedReg(MF, Reg))
+    if (Subtarget->isXRegisterReserved(DwarfRegNum) ||
+        MRI->isReservedReg(MF, Reg))
       Reg = 0;
   }
   if (Reg)

``````````

</details>


https://github.com/llvm/llvm-project/pull/113105