[llvm] [GlobalISel] Preserve original flags of output instructions in matchtable (PR #130937)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-globalisel

Author: Pierre van Houtryve (Pierre-vh)

<details>
<summary>Changes</summary>

We don't have any combine in trunk that uses output MIFlags when using MIR pattenrs, but I tried writing one and noticed that the flags were lost.

The reason is that the MatchTableExecutor was overwriting the flags. 

---
Full diff: https://github.com/llvm/llvm-project/pull/130937.diff


1 Files Affected:

- (modified) llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h (+1-1) 


``````````diff
diff --git a/llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h b/llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h
index 2c57f2b5aa029..654112e86e873 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h
@@ -80,7 +80,7 @@ bool GIMatchTableExecutor::executeMatchTable(
     for (auto MIB : OutMIs) {
       // Set the NoFPExcept flag when no original matched instruction could
       // raise an FP exception, but the new instruction potentially might.
-      uint16_t MIBFlags = Flags;
+      uint16_t MIBFlags = Flags | MIB.getInstr()->getFlags();
       if (NoFPException && MIB->mayRaiseFPException())
         MIBFlags |= MachineInstr::NoFPExcept;
       if (Observer)

``````````

</details>


https://github.com/llvm/llvm-project/pull/130937