[llvm] [DirectX] Implement lowering of Texture Load and Texture .operator[] (PR #193343)

[Helena Kotas via llvm-commits]

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@@ -566,6 +566,73 @@ class OpLowerer {
     });
   }
 
+  [[nodiscard]] bool lowerTextureLoad(Function &F) {
+    IRBuilder<> &IRB = OpBuilder.getIRB();
+    Type *Int32Ty = IRB.getInt32Ty();
+
+    return replaceFunction(F, [&](CallInst *CI) -> Error {
+      IRB.SetInsertPoint(CI);
+
+      Value *Handle =
+          createTmpHandleCast(CI->getArgOperand(0), OpBuilder.getHandleType());
+      Value *Coords = CI->getArgOperand(1);
+      Value *MipLevel = CI->getArgOperand(2);
+      Value *Offsets = CI->getArgOperand(3);
+
+      Type *OldTy = CI->getType();
+      Type *NewRetTy = OpBuilder.getResRetType(OldTy->getScalarType());
+
+      std::array<Value *, 3> CoordArgs = {UndefValue::get(Int32Ty),
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hekota wrote:

These need be `undef` because we are lowering to LLVM 3.7 (=DXIL).

https://github.com/llvm/llvm-project/pull/193343