[llvm] 0b8528e - [instcombine] Adjust style of MemIntrinsic code to be more idiomatic [nfc] (#138715)

[via llvm-commits]

Author: Philip Reames
Date: 2025-05-06T13:19:53-07:00
New Revision: 0b8528e127d898a8bdb0d96c9afc7f3baa4bc3f5

URL: https://github.com/llvm/llvm-project/commit/0b8528e127d898a8bdb0d96c9afc7f3baa4bc3f5
DIFF: https://github.com/llvm/llvm-project/commit/0b8528e127d898a8bdb0d96c9afc7f3baa4bc3f5.diff

LOG: [instcombine] Adjust style of MemIntrinsic code to be more idiomatic [nfc] (#138715)

Use an existing helper function. Remove the use of a local Changed
variable which doesn't seem to interact with surrounding transforms in
any meaningful way. (Both memcpy and memmove are MemTransfer
instructions, so switching from one to the other doesn't change
results.)

Posted for review mostly for a sanity check that I'm not missing
something with the logic around the Change flag.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 844e18dd7d8c5..6ea09ed60c2f8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1671,8 +1671,6 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
   // Intrinsics cannot occur in an invoke or a callbr, so handle them here
   // instead of in visitCallBase.
   if (auto *MI = dyn_cast<AnyMemIntrinsic>(II)) {
-    bool Changed = false;
-
     // memmove/cpy/set of zero bytes is a noop.
     if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
       if (NumBytes->isNullValue())
@@ -1680,29 +1678,8 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
     }
 
     // No other transformations apply to volatile transfers.
-    if (auto *M = dyn_cast<MemIntrinsic>(MI))
-      if (M->isVolatile())
-        return nullptr;
-
-    // If we have a memmove and the source operation is a constant global,
-    // then the source and dest pointers can't alias, so we can change this
-    // into a call to memcpy.
-    if (auto *MMI = dyn_cast<AnyMemMoveInst>(MI)) {
-      if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
-        if (GVSrc->isConstant()) {
-          Module *M = CI.getModule();
-          Intrinsic::ID MemCpyID =
-              isa<AtomicMemMoveInst>(MMI)
-                  ? Intrinsic::memcpy_element_unordered_atomic
-                  : Intrinsic::memcpy;
-          Type *Tys[3] = { CI.getArgOperand(0)->getType(),
-                           CI.getArgOperand(1)->getType(),
-                           CI.getArgOperand(2)->getType() };
-          CI.setCalledFunction(
-              Intrinsic::getOrInsertDeclaration(M, MemCpyID, Tys));
-          Changed = true;
-        }
-    }
+    if (MI->isVolatile())
+      return nullptr;
 
     if (AnyMemTransferInst *MTI = dyn_cast<AnyMemTransferInst>(MI)) {
       // memmove(x,x,size) -> noop.
@@ -1734,7 +1711,25 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
       return eraseInstFromFunction(CI);
     }
 
-    if (Changed) return II;
+    // If we have a memmove and the source operation is a constant global,
+    // then the source and dest pointers can't alias, so we can change this
+    // into a call to memcpy.
+    if (auto *MMI = dyn_cast<AnyMemMoveInst>(MI)) {
+      if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
+        if (GVSrc->isConstant()) {
+          Module *M = CI.getModule();
+          Intrinsic::ID MemCpyID =
+              isa<AtomicMemMoveInst>(MMI)
+                  ? Intrinsic::memcpy_element_unordered_atomic
+                  : Intrinsic::memcpy;
+          Type *Tys[3] = { CI.getArgOperand(0)->getType(),
+                           CI.getArgOperand(1)->getType(),
+                           CI.getArgOperand(2)->getType() };
+          CI.setCalledFunction(
+              Intrinsic::getOrInsertDeclaration(M, MemCpyID, Tys));
+          return II;
+        }
+    }
   }
 
   // For fixed width vector result intrinsics, use the generic demanded vector