[llvm-branch-commits] [llvm] SCEVExpander: Don't look at uses of constants (PR #134691)

[Matt Arsenault via llvm-branch-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/134691

This could be more relaxed, and look for uses of globals in
the same function but no tests apparently depend on that.

>From f543f056aa7e16b1f793d018e0b9c022b006f477 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Mon, 7 Apr 2025 21:56:00 +0700
Subject: [PATCH] SCEVExpander: Don't look at uses of constants

This could be more relaxed, and look for uses of globals in
the same function but no tests apparently depend on that.
---
 .../Utils/ScalarEvolutionExpander.cpp         | 29 ++++++++++---------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
index 41bf202230e22..e25ec6c3b2a58 100644
--- a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
@@ -111,20 +111,23 @@ Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
 
   Value *Ret = nullptr;
 
-  // Check to see if there is already a cast!
-  for (User *U : V->users()) {
-    if (U->getType() != Ty)
-      continue;
-    CastInst *CI = dyn_cast<CastInst>(U);
-    if (!CI || CI->getOpcode() != Op)
-      continue;
+  if (!isa<Constant>(V)) {
+    // Check to see if there is already a cast!
+    for (User *U : V->users()) {
+      if (U->getType() != Ty)
+        continue;
+      CastInst *CI = dyn_cast<CastInst>(U);
+      if (!CI || CI->getOpcode() != Op)
+        continue;
 
-    // Found a suitable cast that is at IP or comes before IP. Use it. Note that
-    // the cast must also properly dominate the Builder's insertion point.
-    if (IP->getParent() == CI->getParent() && &*BIP != CI &&
-        (&*IP == CI || CI->comesBefore(&*IP))) {
-      Ret = CI;
-      break;
+      // Found a suitable cast that is at IP or comes before IP. Use it. Note
+      // that the cast must also properly dominate the Builder's insertion
+      // point.
+      if (IP->getParent() == CI->getParent() && &*BIP != CI &&
+          (&*IP == CI || CI->comesBefore(&*IP))) {
+        Ret = CI;
+        break;
+      }
     }
   }