[Backport to 17] Enhance handling of umul_with_overflow in reverse translation (#3524)

Co-authored-by: Dmitry Sidorov <dmitry.sidorov@intel.com>

Author: vmaksimo

lib/SPIRV/SPIRVReader.cpp

@@ -3420,6 +3420,20 @@ Function *SPIRVToLLVM::transFunction(SPIRVFunction *BF, unsigned AS) {
                                   {FT->getParamType(0), FT->getParamType(2)})
             ->getName();
   }
+
+  // Special handling for spirv.llvm_umul_with_overflow_* functions
+  // These were created during forward translation by lowering intrinsics.
+  // During reverse translation, we replace them with intrinsic calls.
+  if (FuncNameRef.starts_with("spirv.llvm_umul_with_overflow_")) {
+    Type *OverloadTy = FT->getParamType(0);
+    Function *F = Intrinsic::getDeclaration(M, Intrinsic::umul_with_overflow,
+                                            {OverloadTy});
+    F = cast<Function>(mapValue(BF, F));
+    mapFunction(BF, F);
+    return F; // Skip body translation - intrinsic will be used instead
+  }
+
+  // Normal function handling.
   if (FuncNameRef.consume_front("spirv.")) {
     FuncNameRef.consume_back(".volatile");
     FuncName = FuncNameRef.str();
@@ -3428,21 +3442,12 @@ Function *SPIRVToLLVM::transFunction(SPIRVFunction *BF, unsigned AS) {
   Function *F = M->getFunction(FuncName);
   if (!F)
     F = Function::Create(FT, Linkage, AS, FuncName, M);
+
   F = cast<Function>(mapValue(BF, F));
   mapFunction(BF, F);
 
   if (F->isIntrinsic()) {
-    if (F->getIntrinsicID() != Intrinsic::umul_with_overflow)
-      return F;
-    std::string Name = F->getName().str();
-    auto *ST = cast<StructType>(F->getReturnType());
-    auto *FT = F->getFunctionType();
-    auto *NewST = StructType::get(ST->getContext(), ST->elements());
-    auto *NewFT = FunctionType::get(NewST, FT->params(), FT->isVarArg());
-    F->setName("old_" + Name);
-    auto *NewFn = Function::Create(NewFT, F->getLinkage(), F->getAddressSpace(),
-                                   Name, F->getParent());
-    return NewFn;
+    return F;
   }
 
   F->setCallingConv(IsKernel ? CallingConv::SPIR_KERNEL

test/llvm-intrinsics/umul.with.overflow.ll

@@ -6,7 +6,8 @@
 ; On LLVM level, we'll check that the intrinsics were generated again in reverse
 ; translation, replacing the SPIR-V level implementations.
 ; RUN: llvm-dis %t.rev.bc -o - | FileCheck %s --check-prefix=CHECK-LLVM \
-; RUN:   "--implicit-check-not=declare {{.*}} @spirv.llvm_umul_with_overflow_{{.*}}"
+; RUN:   "--implicit-check-not=declare {{.*}} @spirv.llvm_umul_with_overflow_{{.*}}" \
+; RUN:   "--implicit-check-not=old_llvm.umul.with.overflow.{{.*}}"
 
 ; CHECK-SPIRV: Name [[NAME_UMUL_FUNC_8:[0-9]+]] "spirv.llvm_umul_with_overflow_i8"
 ; CHECK-SPIRV: Name [[NAME_UMUL_FUNC_32:[0-9]+]] "spirv.llvm_umul_with_overflow_i32"
@@ -25,6 +26,8 @@ entry:
   %umul.value = extractvalue { i8, i1 } %umul, 0
   %storemerge = select i1 %cmp, i8 0, i8 %umul.value
   store i8 %storemerge, i8* %c, align 1, !tbaa !2
+  ; This test case verifies we don't leave any artifact calls behind (e.g. old_llvm.umul.with.overflow.i8).
+  %umul2 = tail call { i8, i1 } @llvm.umul.with.overflow.i8(i8 %a, i8 %b)
   ret void
 }