[llvm] [RISCV] RISCVISD::SELECT_CC is for integer comparisons only which can't create poison (PR #151943)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-risc-v

Author: Simon Pilgrim (RKSimon)

<details>
<summary>Changes</summary>

The result type is irrelevant - its the comparison type that matters

---
Full diff: https://github.com/llvm/llvm-project/pull/151943.diff


1 Files Affected:

- (modified) llvm/lib/Target/RISCV/RISCVISelLowering.cpp (+4-5) 


``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index b6d1ee8bc3050..9e1deea93b971 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -21478,11 +21478,10 @@ bool RISCVTargetLowering::canCreateUndefOrPoisonForTargetNode(
   // TODO: Add more target nodes.
   switch (Op.getOpcode()) {
   case RISCVISD::SELECT_CC:
-    // Integer select_cc cannot create poison.
-    // TODO: What are the FP poison semantics?
-    // TODO: This instruction blocks poison from the unselected operand, can
-    // we do anything with that?
-    return !Op.getValueType().isInteger();
+    // Integer comparisons cannot create poison.
+    assert(Op.getOperand(0).getValueType().isInteger() &&
+           "RISCVISD::SELECT_CC only compares integers");
+    return false;
   }
   return TargetLowering::canCreateUndefOrPoisonForTargetNode(
       Op, DemandedElts, DAG, PoisonOnly, ConsiderFlags, Depth);

``````````

</details>


https://github.com/llvm/llvm-project/pull/151943