Fix miscompilation when adding a 64-bit constant to a symbol (#4283)

Fixes #4264

Author: zyedidia

gen/toir.cpp

@@ -847,15 +847,21 @@ class ToElemVisitor : public Visitor {
         uint64_t elemSize = gDataLayout->getTypeAllocSize(elemType);
         if (e->offset % elemSize == 0) {
           // We can turn this into a "nice" GEP.
-          offsetValue = DtoGEP1(DtoType(base->type), baseValue, e->offset / elemSize);
+          if (elemType->isStructTy()) {
+            // LLVM getelementptr requires that offsets are 32-bit constants
+            // when the base type is a struct.
+            offsetValue = DtoGEP1(DtoType(base->type), baseValue, e->offset / elemSize);
+          } else {
+            offsetValue = DtoGEP1i64(DtoType(base->type), baseValue, e->offset / elemSize);
+          }
         }
       }
 
       if (!offsetValue) {
         // Offset isn't a multiple of base type size, just cast to i8* and
         // apply the byte offset.
         offsetValue =
-            DtoGEP1(LLType::getInt8Ty(gIR->context()),
+            DtoGEP1i64(LLType::getInt8Ty(gIR->context()),
                     DtoBitCast(baseValue, getVoidPtrType()), e->offset);
       }
     }

gen/tollvm.cpp

@@ -385,6 +385,11 @@ LLConstant *DtoGEP(LLType *pointeeTy, LLConstant *ptr, unsigned i0,
                                               /* InBounds = */ true);
 }
 
+LLValue *DtoGEP1i64(LLType *pointeeTy, LLValue *ptr, uint64_t i0, const char *name,
+                    llvm::BasicBlock *bb) {
+  return DtoGEP(pointeeTy, ptr, DtoConstUlong(i0), name, bb);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 void DtoMemSet(LLValue *dst, LLValue *val, LLValue *nbytes, unsigned align) {
@@ -450,6 +455,12 @@ LLValue *DtoMemCmp(LLValue *lhs, LLValue *rhs, LLValue *nbytes) {
 llvm::ConstantInt *DtoConstSize_t(uint64_t i) {
   return LLConstantInt::get(DtoSize_t(), i, false);
 }
+llvm::ConstantInt *DtoConstUlong(uint64_t i) {
+  return LLConstantInt::get(LLType::getInt64Ty(gIR->context()), i, false);
+}
+llvm::ConstantInt *DtoConstLong(int64_t i) {
+  return LLConstantInt::get(LLType::getInt64Ty(gIR->context()), i, true);
+}
 llvm::ConstantInt *DtoConstUint(unsigned i) {
   return LLConstantInt::get(LLType::getInt32Ty(gIR->context()), i, false);
 }

gen/tollvm.h

@@ -95,8 +95,13 @@ LLValue *DtoGEP(LLType *pointeeTy, LLValue *ptr, unsigned i0, unsigned i1,
 LLConstant *DtoGEP(LLType *pointeeTy, LLConstant *ptr, unsigned i0,
                    unsigned i1);
 
+LLValue *DtoGEP1i64(LLType *pointeeTy, LLValue *ptr, uint64_t i0,
+                    const char *name = "", llvm::BasicBlock *bb = nullptr);
+
 // to constant helpers
 LLConstantInt *DtoConstSize_t(uint64_t);
+LLConstantInt *DtoConstUlong(uint64_t i);
+LLConstantInt *DtoConstLong(int64_t i);
 LLConstantInt *DtoConstUint(unsigned i);
 LLConstantInt *DtoConstInt(int i);
 LLConstantInt *DtoConstUbyte(unsigned char i);

tests/codegen/gh2865.d

@@ -2,7 +2,7 @@
 
 void foo()
 {
-    // CHECK: %1 = getelementptr inbounds i8,{{.*}}_D6gh28653fooFZv{{.*}}, i32 -10
+    // CHECK: %1 = getelementptr inbounds i8,{{.*}}_D6gh28653fooFZv{{.*}}, i64 -10
     // CHECK-NEXT: %2 = ptrtoint {{i8\*|ptr}} %1 to i{{32|64}}
     auto addr = (cast(size_t) &foo) - 10;
 }

tests/codegen/gh4264.d

@@ -0,0 +1,6 @@
+// RUN: %ldc -run %s
+
+enum offset = 0xFFFF_FFFF_0000_0000UL;
+void main() {
+    assert((cast(ulong)&main) != (cast(ulong)&main + offset));
+}