Fix incorrect translation of calls to a builtin that returns a struct…

…ure (#2722)

Fix issue #2721: Incorrect translation of calls to a builtin that returns a structure: create just one load, and account for a special case when Translator prepared a well-known pattern (store/load) for itself.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@dc1221cd83e67ef

llvm-spirv/lib/SPIRV/SPIRVUtil.cpp

@@ -2229,8 +2229,9 @@ bool postProcessBuiltinReturningStruct(Function *F) {
  Builder.SetInsertPoint(CI);
  SmallVector<User *> Users(CI->users());
  Value *A = nullptr;
+ StoreInst *SI = nullptr;
  for (auto *U : Users) {
- if (auto *SI = dyn_cast<StoreInst>(U)) {
+ if ((SI = dyn_cast<StoreInst>(U)) != nullptr) {
  A = SI->getPointerOperand();
  InstToRemove.push_back(SI);
  break;
@@ -2253,9 +2254,14 @@ bool postProcessBuiltinReturningStruct(Function *F) {
  CallInst *NewCI = Builder.CreateCall(NewF, Args, CI->getName());
  NewCI->addParamAttr(0, SretAttr);
  NewCI->setCallingConv(CI->getCallingConv());
- SmallVector<User *> CIUsers(CI->users());
- for (auto *CIUser : CIUsers) {
- CIUser->replaceUsesOfWith(CI, A);
+ SmallVector<User *, 32> UsersToReplace;
+ for (auto *U : Users)
+ if (U != SI)
+ UsersToReplace.push_back(U);
+ if (UsersToReplace.size() > 0) {
+ auto *LI = Builder.CreateLoad(F->getReturnType(), A);
+ for (auto *U : UsersToReplace)
+ U->replaceUsesOfWith(CI, LI);
  }
  InstToRemove.push_back(CI);
  }

llvm-spirv/test/builtin_returns_struct.spvasm

@@ -0,0 +1,52 @@
+; REQUIRES: spirv-as
+; RUN: spirv-as --target-env spv1.0 -o %t.spv %s
+; RUN: spirv-val %t.spv
+; RUN: llvm-spirv -r -o - %t.spv | llvm-dis | FileCheck %s
+
+ OpCapability Kernel
+ OpCapability Addresses
+ OpCapability Int8
+ OpCapability GenericPointer
+ OpCapability Linkage
+ %1 = OpExtInstImport "OpenCL.std"
+ OpMemoryModel Physical64 OpenCL
+ OpSource OpenCL_CPP 100000
+ OpName %a "a"
+ OpName %p "p"
+ OpName %foo "foo"
+ OpName %e "e"
+ OpName %math "math"
+ OpName %ov "ov"
+ OpDecorate %foo LinkageAttributes "foo" Export
+ %uint = OpTypeInt 32 0
+ %uchar = OpTypeInt 8 0
+%_ptr_Generic_uchar = OpTypePointer Generic %uchar
+ %5 = OpTypeFunction %uint %uint %_ptr_Generic_uchar
+ %bool = OpTypeBool
+ %_struct_7 = OpTypeStruct %uint %uint
+ %uint_1 = OpConstant %uint 1
+ %uchar_42 = OpConstant %uchar 42
+ %10 = OpConstantNull %uint
+ %foo = OpFunction %uint None %5
+ %a = OpFunctionParameter %uint
+ %p = OpFunctionParameter %_ptr_Generic_uchar
+ %19 = OpLabel
+ OpBranch %20
+ %20 = OpLabel
+ %e = OpPhi %uint %a %19 %math %21
+ %16 = OpIAddCarry %_struct_7 %e %uint_1
+ %math = OpCompositeExtract %uint %16 0
+ %17 = OpCompositeExtract %uint %16 1
+ %ov = OpINotEqual %bool %17 %10
+ OpBranchConditional %ov %22 %21
+ %21 = OpLabel
+ OpStore %p %uchar_42 Aligned 1
+ OpBranch %20
+ %22 = OpLabel
+ OpReturnValue %math
+ OpFunctionEnd
+
+; CHECK: %[[#Var:]] = alloca %structtype, align 8
+; CHECK: call spir_func void @_Z17__spirv_IAddCarryii(ptr sret(%structtype) %[[#Var:]]
+; CHECK: %[[#Load:]] = load %structtype, ptr %[[#Var]], align 4
+; CHECK-2: extractvalue %structtype %[[#Load:]]