[llvm-branch-commits] [llvm] GlobalISel: Use MIPatternMatch in GIMatchTableExecutor (PR #216601)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-globalisel

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

Replace the getVRegDef + opcode-check idiom in isBaseWithConstantOffset with
mi_match using m_GPtrAdd and m_GConstant.

Co-authored-by: Claude (Opus 4.8) <noreply@<!-- -->anthropic.com>

---
Full diff: https://github.com/llvm/llvm-project/pull/216601.diff


1 Files Affected:

- (modified) llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp (+6-8) 


``````````diff
diff --git a/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp b/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp
index 1edfc09310554..d06f64a72922a 100644
--- a/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/GIMatchTableExecutor.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/CodeGen/GlobalISel/GIMatchTableExecutor.h"
+#include "llvm/CodeGen/GlobalISel/MIPatternMatch.h"
 #include "llvm/CodeGen/GlobalISel/Utils.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineOperand.h"
@@ -20,6 +21,7 @@
 #define DEBUG_TYPE "gi-match-table-executor"
 
 using namespace llvm;
+using namespace MIPatternMatch;
 
 GIMatchTableExecutor::MatcherState::MatcherState(unsigned MaxRenderers)
     : Renderers(MaxRenderers) {}
@@ -47,16 +49,12 @@ bool GIMatchTableExecutor::isBaseWithConstantOffset(
   if (!Root.isReg())
     return false;
 
-  MachineInstr *RootI = MRI.getVRegDef(Root.getReg());
-  if (RootI->getOpcode() != TargetOpcode::G_PTR_ADD)
+  GPtrAdd *RootI;
+  if (!mi_match(Root.getReg(), MRI, m_GPtrAdd(RootI)))
     return false;
 
-  MachineOperand &RHS = RootI->getOperand(2);
-  MachineInstr *RHSI = MRI.getVRegDef(RHS.getReg());
-  if (RHSI->getOpcode() != TargetOpcode::G_CONSTANT)
-    return false;
-
-  return true;
+  GConstant *RHSI;
+  return mi_match(RootI->getOffsetReg(), MRI, m_GConstant(RHSI));
 }
 
 bool GIMatchTableExecutor::isObviouslySafeToFold(MachineInstr &MI,

``````````

</details>


https://github.com/llvm/llvm-project/pull/216601