[SPIRV][HLSL] Fix assert with cbuffers through constexpr

The comment here pointed out that RAUW would fall over given a
constantexpr, but then proceeded to just do what RAUW does by hand,
which falls over in the same way. Instead, convert constantexprs
involving cbuffer globals to instructions before processing them.

The test update just modifies the existing cbuffer test, since it
implied it was trying to test this exact case anyways.

Author: bogner

llvm/lib/Target/SPIRV/SPIRVCBufferAccess.cpp

@@ -35,6 +35,7 @@
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/IntrinsicsSPIRV.h"
 #include "llvm/IR/Module.h"
+#include "llvm/IR/ReplaceConstant.h"
 
 #define DEBUG_TYPE "spirv-cbuffer-access"
 using namespace llvm;
@@ -57,6 +58,12 @@ static bool replaceCBufferAccesses(Module &M) {
   if (!CBufMD)
     return false;
 
+  SmallVector<Constant *> CBufferGlobals;
+  for (const hlsl::CBufferMapping &Mapping : *CBufMD)
+    for (const hlsl::CBufferMember &Member : Mapping.Members)
+      CBufferGlobals.push_back(Member.GV);
+  convertUsersOfConstantsToInstructions(CBufferGlobals);
+
   for (const hlsl::CBufferMapping &Mapping : *CBufMD) {
     Instruction *HandleDef = findHandleDef(Mapping.Handle);
     if (!HandleDef) {
@@ -80,12 +87,7 @@ static bool replaceCBufferAccesses(Module &M) {
       Value *GetPointerCall = Builder.CreateIntrinsic(
           PtrType, Intrinsic::spv_resource_getpointer, {HandleDef, IndexVal});
 
-      // We cannot use replaceAllUsesWith here because some uses may be
-      // ConstantExprs, which cannot be replaced with non-constants.
-      SmallVector<User *, 4> Users(MemberGV->users());
-      for (User *U : Users) {
-        U->replaceUsesOfWith(MemberGV, GetPointerCall);
-      }
+      MemberGV->replaceAllUsesWith(GetPointerCall);
     }
   }
 

llvm/test/CodeGen/SPIRV/hlsl-resources/cbuffer.ll

@@ -1,5 +1,5 @@
 ; RUN: llc -O0 -verify-machineinstrs -mtriple=spirv1.6-vulkan1.3-library %s -o - | FileCheck %s
-; Test that uses of cbuffer members inside ConstantExprs are handled correctly.
+; Test that uses of cbuffer members are handled correctly.
 
 ; CHECK-DAG: OpDecorate %[[MyCBuffer:[0-9]+]] DescriptorSet 0
 ; CHECK-DAG: OpDecorate %[[MyCBuffer]] Binding 0
@@ -37,10 +37,8 @@ entry:
 ; CHECK: %[[tmp_ptr:[0-9]+]] = OpAccessChain {{%[0-9]+}} %[[tmp]] %[[uint_0]] %[[uint_0]]
 ; CHECK: %[[v_ptr:.+]] = OpAccessChain %[[_ptr_Uniform_v4float]] %[[tmp]] %[[uint_0]] %[[uint_1]]
 ; CHECK: %[[s_ptr_gep:[0-9]+]] = OpInBoundsAccessChain %[[_ptr_Uniform_float]] %[[tmp_ptr]] %[[uint_0]] %[[uint_1]]
-  %gep = getelementptr inbounds %MyStruct, ptr addrspace(12) @s, i32 0, i32 0, i32 1
-
 ; CHECK: %[[s_val:.+]] = OpLoad %[[float]] %[[s_ptr_gep]]
-  %load_from_gep = load float, ptr addrspace(12) %gep, align 4
+  %load_from_gep = load float, ptr addrspace(12) getelementptr inbounds (%MyStruct, ptr addrspace(12) @s, i32 0, i32 0, i32 1), align 4
 
 ; CHECK: %[[v_val:.+]] = OpLoad %[[v4float]] %[[v_ptr]]
   %load_v = load <4 x float>, ptr addrspace(12) @v, align 16