[llvm] [GlobalISel] Clamp out-of-range G_EXTRACT_VECTOR_ELT constant indices when converting them into loads. (PR #82460)

[Jessica Paquette via llvm-commits]

================
@@ -3971,14 +3971,19 @@ LegalizerHelper::createStackTemporary(TypeSize Bytes, Align Alignment,
   return MIRBuilder.buildFrameIndex(FramePtrTy, FrameIdx);
 }
 
-static Register clampDynamicVectorIndex(MachineIRBuilder &B, Register IdxReg,
-                                        LLT VecTy) {
-  int64_t IdxVal;
-  if (mi_match(IdxReg, *B.getMRI(), m_ICst(IdxVal)))
-    return IdxReg;
-
+static Register clampVectorIndex(MachineIRBuilder &B, Register IdxReg,
+                                 LLT VecTy) {
   LLT IdxTy = B.getMRI()->getType(IdxReg);
   unsigned NElts = VecTy.getNumElements();
+
+  int64_t IdxVal;
+  if (mi_match(IdxReg, *B.getMRI(), m_ICst(IdxVal))) {
+    if (IdxVal < VecTy.getNumElements()) {
----------------
ornata wrote:

style nit on braces

https://github.com/llvm/llvm-project/pull/82460