[llvm] [nfc][InstCombine]Find PHI incoming block by operand number (PR #93249)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Mingming Liu (minglotus-6)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/93249.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstructionCombining.cpp (+15-14) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 6c25ff215c375..b0361db1708f9 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -5000,26 +5000,27 @@ bool InstCombinerImpl::run() {
       BasicBlock *UserParent = nullptr;
       unsigned NumUsers = 0;
 
-      for (auto *U : I->users()) {
-        if (U->isDroppable())
+      for (Use &U : I->uses()) {
+        User *User = U.getUser();
+        if (User->isDroppable())
           continue;
         if (NumUsers > MaxSinkNumUsers)
           return std::nullopt;
 
-        Instruction *UserInst = cast<Instruction>(U);
+        Instruction *UserInst = cast<Instruction>(User);
         // Special handling for Phi nodes - get the block the use occurs in.
         if (PHINode *PN = dyn_cast<PHINode>(UserInst)) {
-          for (unsigned i = 0; i < PN->getNumIncomingValues(); i++) {
-            if (PN->getIncomingValue(i) == I) {
-              // Bail out if we have uses in different blocks. We don't do any
-              // sophisticated analysis (i.e finding NearestCommonDominator of
-              // these use blocks).
-              if (UserParent && UserParent != PN->getIncomingBlock(i))
-                return std::nullopt;
-              UserParent = PN->getIncomingBlock(i);
-            }
-          }
-          assert(UserParent && "expected to find user block!");
+          unsigned Num =
+              PHINode::getIncomingValueNumForOperand(U.getOperandNo());
+          assert(PN->getIncomingValue(Num) == I && "Expect from def-use chain");
+
+          // Bail out if we have uses in different blocks. We don't do any
+          // sophisticated analysis (i.e finding NearestCommonDominator of
+          // these use blocks).
+          BasicBlock* IncomingBlock = PN->getIncomingBlock(Num);
+          if (UserParent && UserParent != IncomingBlock)
+            return std::nullopt;
+          UserParent = PN->getIncomingBlock(Num);
         } else {
           if (UserParent && UserParent != UserInst->getParent())
             return std::nullopt;

``````````

</details>


https://github.com/llvm/llvm-project/pull/93249