[NVPTX] Implement isTruncateFree and isZExtFree for i32/i64 Optimizations

[SergeantCooper]

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

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[llvmbot]

@llvm/pr-subscribers-backend-nvptx

Author: None (Quark-69)

Changes

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 --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;

[AlexMaclean]

Could you please add some lit tests to this PR to demonstrate what the intended impact of this change is?

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⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff b24650e814e55d90acfc40acf045456c98f32b9c 1361e2c072dc60162f5de0992d248eebd3156573 --extensions h,cpp -- llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp llvm/lib/Target/NVPTX/NVPTXISelLowering.h

View the diff from clang-format here.

diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.h b/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
index 57dc5b8fad..427deb4a65 100644
--- a/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
+++ b/llvm/lib/Target/NVPTX/NVPTXISelLowering.h
@@ -612,9 +612,9 @@ public:
     return true;
   }
 
-   bool isTruncateFree(EVT FromVT, EVT ToVT) const override;
+  bool isTruncateFree(EVT FromVT, EVT ToVT) const override;
 
-   bool isZExtFree(EVT FromVT, EVT ToVT) const override;
+  bool isZExtFree(EVT FromVT, EVT ToVT) const override;
 
 private:
   const NVPTXSubtarget &STI; // cache the subtarget here