[GlobalIsel][AArch64] fix out of range access in regbankselect

[tschuett]

Fixes #92062

[llvmbot]

@llvm/pr-subscribers-llvm-globalisel

@llvm/pr-subscribers-backend-aarch64

Author: Thorsten Schütt (tschuett)

Changes

Fixes #92062

---

Full diff: https://github.com/llvm/llvm-project/pull/92072.diff

2 Files Affected:

• (modified) llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp (+4-1)
• (added) llvm/test/CodeGen/AArch64/pr92062.ll (+21)

diff --git a/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp b/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
index 44ba9f0429e67..7785e020eaaf1 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
@@ -600,8 +600,11 @@ bool AArch64RegisterBankInfo::isLoadFromFPType(const MachineInstr &MI) const {
     EltTy = GV->getValueType();
     // Look at the first element of the struct to determine the type we are
     // loading
-    while (StructType *StructEltTy = dyn_cast<StructType>(EltTy))
+    while (StructType *StructEltTy = dyn_cast<StructType>(EltTy)) {
+      if (StructEltTy->getNumElements() == 0)
+        break;
       EltTy = StructEltTy->getTypeAtIndex(0U);
+    }
     // Look at the first element of the array to determine its type
     if (isa<ArrayType>(EltTy))
       EltTy = EltTy->getArrayElementType();
diff --git a/llvm/test/CodeGen/AArch64/pr92062.ll b/llvm/test/CodeGen/AArch64/pr92062.ll
new file mode 100644
index 0000000000000..0f911d2571f6d
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/pr92062.ll
@@ -0,0 +1,21 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -mtriple=aarch64 -O0 -global-isel -global-isel-abort=2 -verify-machineinstrs %s -o - 2>&1 | FileCheck %s
+
+target triple = "arm64"
+
+@p = external global { {}, { ptr } }
+
+define void @foo() {
+; CHECK-LABEL: foo:
+; CHECK:       // %bb.0: // %bb
+; CHECK-NEXT:    adrp x8, :got:p
+; CHECK-NEXT:    ldr x8, [x8, :got_lo12:p]
+; CHECK-NEXT:    ldr x8, [x8]
+; CHECK-NEXT:    mov x9, xzr
+; CHECK-NEXT:    str x8, [x9]
+; CHECK-NEXT:    ret
+bb:
+  %i1 = load ptr, ptr @p, align 8
+  store ptr %i1, ptr null, align 8
+  ret void
+}

[dianqk]

Thank you for the quick fix.

[dianqk]

Suggested change

	// Look at the first element of the struct to determine the type we are
	// Look at the first valid element of the struct to determine the type we are

It seems we should also update the comment.