[llvm] [AArch64] merge index address with large offset into base address (PR #75343)

[David Green via llvm-commits]

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@@ -722,6 +781,40 @@ static bool isMergeableLdStUpdate(MachineInstr &MI) {
   }
 }
 
+// Make sure this is a reg+reg Ld/St
+static bool isMergeableIndexLdSt(MachineInstr &MI, int &Scale) {
+  unsigned Opc = MI.getOpcode();
+  switch (Opc) {
+  default:
+    return false;
+  // Scaled instructions.
+  // TODO: Add more index address stores.
+  case AArch64::LDRBroX:
+  case AArch64::LDRBBroX:
+  case AArch64::LDRSBXroX:
+  case AArch64::LDRSBWroX:
+    Scale = 1;
+    return true;
+  case AArch64::LDRHroX:
+  case AArch64::LDRHHroX:
+  case AArch64::LDRSHXroX:
+  case AArch64::LDRSHWroX:
+    Scale = 2;
+    return true;
+  case AArch64::LDRWroX:
+  case AArch64::LDRSWroX:
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davemgreen wrote:

Should there be LDRSroX too?

https://github.com/llvm/llvm-project/pull/75343