[llvm] [InstCombine] Remove redundant align 1 assumptions. (PR #160695)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Florian Hahn (fhahn)

<details>
<summary>Changes</summary>

It seems like we have a bunch of align 1 assumptions in practice and unless I am missing something they should not add any value.

See https://github.com/dtcxzyw/llvm-opt-benchmark/pull/2861/files

---
Full diff: https://github.com/llvm/llvm-project/pull/160695.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp (+3) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 6ad493772d170..896548ddd9931 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3412,6 +3412,9 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
             !isPowerOf2_64(RK.ArgValue) || !isa<ConstantInt>(RK.IRArgValue))
           continue;
 
+        if (RK.ArgValue == 1)
+          return CallBase::removeOperandBundle(II, OBU.getTagID());
+
         // Don't try to remove align assumptions for pointers derived from
         // arguments. We might lose information if the function gets inline and
         // the align argument attribute disappears.

``````````

</details>


https://github.com/llvm/llvm-project/pull/160695