[llvm] [NVPTX] Implement isTruncateFree and isZExtFree for i32/i64 Optimizations (PR #114601)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-nvptx

Author: None (Quark-69)

<details>
<summary>Changes</summary>

Implemented isTruncateFree and isZExtFree virtual functions in NVPTXTargetLowering to optimize i32/i64 truncation and zero-extension operations.

---
Full diff: https://github.com/llvm/llvm-project/pull/114601.diff


2 Files Affected:

- (modified) llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp (+8) 
- (modified) llvm/lib/Target/NVPTX/NVPTXISelLowering.h (+4) 


``````````diff
diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
index 379a4a77647079..2f2f204d0d36f8 100644
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -3285,6 +3285,14 @@ bool NVPTXTargetLowering::splitValueIntoRegisterParts(
   return false;
 }
 
+bool llvm::NVPTXTargetLowering::isTruncateFree(EVT FromVT, EVT ToVT) const {
+  return (FromVT.getSimpleVT() == MVT::i64 && ToVT.getSimpleVT() == MVT::i32);
+}
+
+bool llvm::NVPTXTargetLowering::isZExtFree(EVT FromVT, EVT ToVT) const {
+  return (FromVT.getSimpleVT() == MVT::i32 && ToVT.getSimpleVT() == MVT::i64);
+}
+
 // This creates target external symbol for a function parameter.
 // Name of the symbol is composed from its index and the function name.
 // Negative index corresponds to special parameter (unsized array) used for
diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.h b/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
index 13153f4830b695..57dc5b8fad4058 100644
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
@@ -612,6 +612,10 @@ class NVPTXTargetLowering : public TargetLowering {
     return true;
   }
 
+   bool isTruncateFree(EVT FromVT, EVT ToVT) const override;
+
+   bool isZExtFree(EVT FromVT, EVT ToVT) const override;
+
 private:
   const NVPTXSubtarget &STI; // cache the subtarget here
   SDValue getParamSymbol(SelectionDAG &DAG, int idx, EVT) const;

``````````

</details>


https://github.com/llvm/llvm-project/pull/114601