[GISel]: Fix incorrect IRTranslation while translating null pointer types

[aditya_nandakumar]

Summary

Currently IRTranslator produces
%vreg17<def>(p0) = G_CONSTANT 0;

instead we should build
%vreg16(s64) = G_CONSTANT 0
%vreg17(p0) = G_INTTOPTR %vreg16

[aemerson]

LGTM.

[aditya_nandakumar]

Thanks @aemerson ..

[aditya_nandakumar]

Committed in r328218.

lib/CodeGen/GlobalISel/IRTranslator.cpp

 
 bool IRTranslator::translate(const Constant &C, unsigned Reg) {
   if (auto CI = dyn_cast<ConstantInt>(&C))
     EntryBuilder.buildConstant(Reg, *CI);
   else if (auto CF = dyn_cast<ConstantFP>(&C))
     EntryBuilder.buildFConstant(Reg, *CF);
   else if (isa<UndefValue>(C))
     EntryBuilder.buildUndef(Reg);
-  else if (isa<ConstantPointerNull>(C))
-    EntryBuilder.buildConstant(Reg, 0);
-  else if (auto GV = dyn_cast<GlobalValue>(&C))
+  else if (isa<ConstantPointerNull>(C)) {
+    // As we are trying to build a constant val of 0 into a pointer,
+    // insert a cast to make them correct with respect to types.
+    unsigned NullSize = DL->getTypeSizeInBits(C.getType());
+    auto *ZeroTy = Type::getIntNTy(C.getContext(), NullSize);
+    auto *ZeroVal = ConstantInt::get(ZeroTy, 0);
+    unsigned ZeroReg = getOrCreateVReg(*ZeroVal);
+    EntryBuilder.buildCast(Reg, ZeroReg);
+  } else if (auto GV = dyn_cast<GlobalValue>(&C))
     EntryBuilder.buildGlobalValue(Reg, GV);
   else if (auto CAZ = dyn_cast<ConstantAggregateZero>(&C)) {
     if (!CAZ->getType()->isVectorTy())
       return false;
     // Return the scalar if it is a <1 x Ty> vector.
     if (CAZ->getNumElements() == 1)
       return translate(*CAZ->getElementValue(0u), Reg);
     std::vector<unsigned> Ops;

test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll

block:
   store i16* %dummy, i16** undef
   ret void
 
 end:
   %vec = load <2 x i16*>, <2 x i16*>* undef
   br label %block
 }
 
-; FALLBACK-WITH-REPORT-ERR: remark: <unknown>:0:0: unable to legalize instruction: G_STORE %0:_(<2 x p0>), %4:_(p0) :: (store 16 into `<2 x i16*>* undef`) (in function: vector_of_pointers_insertelement)
+; FALLBACK-WITH-REPORT-ERR: remark: <unknown>:0:0: unable to legalize instruction: G_STORE %0:_(<2 x p0>), %5:_(p0) :: (store 16 into `<2 x i16*>* undef`) (in function: vector_of_pointers_insertelement)
 ; FALLBACK-WITH-REPORT-ERR: warning: Instruction selection used fallback path for vector_of_pointers_insertelement
 ; FALLBACK-WITH-REPORT-OUT-LABEL: vector_of_pointers_insertelement:
 define void @vector_of_pointers_insertelement() {
   br label %end
 
 block:
   %dummy = insertelement <2 x i16*> %vec, i16* null, i32 0
   store <2 x i16*> %dummy, <2 x i16*>* undef

test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll

 ; CHECK-NEXT: $w0 = COPY [[RES]]
 ; CHECK-NEXT: RET_ReallyLR implicit $w0
 define i32 @test_urem(i32 %arg1, i32 %arg2) {
   %res = urem i32 %arg1, %arg2
   ret i32 %res
 }
 
 ; CHECK-LABEL: name: test_constant_null
-; CHECK: [[NULL:%[0-9]+]]:_(p0) = G_CONSTANT i64 0
+; CHECK: [[ZERO:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+; CHECK: [[NULL:%[0-9]+]]:_(p0) = G_INTTOPTR [[ZERO]]
 ; CHECK: $x0 = COPY [[NULL]]
 define i8* @test_constant_null() {
   ret i8* null
 }
 
 ; CHECK-LABEL: name: test_struct_memops
 ; CHECK: [[ADDR:%[0-9]+]]:_(p0) = COPY $x0
 ; CHECK: [[VAL:%[0-9]+]]:_(s64) = G_LOAD [[ADDR]](p0) :: (load 8 from  %ir.addr, align 4)

test/CodeGen/AArch64/GlobalISel/call-translator.ll

define void @test_stack_slots([8 x i64], i64 %lhs, i64 %rhs, i64* %addr) {
   %sum = add i64 %lhs, %rhs
   store i64 %sum, i64* %addr
   ret void
 }
 
 ; CHECK-LABEL: name: test_call_stack
 ; CHECK: [[C42:%[0-9]+]]:_(s64) = G_CONSTANT i64 42
 ; CHECK: [[C12:%[0-9]+]]:_(s64) = G_CONSTANT i64 12
-; CHECK: [[PTR:%[0-9]+]]:_(p0) = G_CONSTANT i64 0
+; CHECK: [[ZERO:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+; CHECK: [[PTR:%[0-9]+]]:_(p0) = G_INTTOPTR [[ZERO]]
 ; CHECK: ADJCALLSTACKDOWN 24, 0, implicit-def $sp, implicit $sp
 ; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[C42_OFFS:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
 ; CHECK: [[C42_LOC:%[0-9]+]]:_(p0) = G_GEP [[SP]], [[C42_OFFS]](s64)
 ; CHECK: G_STORE [[C42]](s64), [[C42_LOC]](p0) :: (store 8 into stack, align 0)
 ; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[C12_OFFS:%[0-9]+]]:_(s64) = G_CONSTANT i64 8
 ; CHECK: [[C12_LOC:%[0-9]+]]:_(p0) = G_GEP [[SP]], [[C12_OFFS]](s64)

test/CodeGen/AArch64/GlobalISel/irtranslator-exceptions.ll

broken:
   ret void
 
 continue:
   ret void
 }
 
 ; CHECK-LABEL: name: test_invoke_varargs
 
-; CHECK: [[NULL:%[0-9]+]]:_(p0) = G_CONSTANT i64 0
+; CHECK: [[ZERO:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+; CHECK: [[NULL:%[0-9]+]]:_(p0) = G_INTTOPTR [[ZERO]]
 ; CHECK: [[ANSWER:%[0-9]+]]:_(s32) = G_CONSTANT i32 42
 ; CHECK: [[ONE:%[0-9]+]]:_(s32) = G_FCONSTANT float 1.0
 
 ; CHECK: $x0 = COPY [[NULL]]
 
 ; CHECK: [[SP:%[0-9]+]]:_(p0) = COPY $sp
 ; CHECK: [[OFFSET:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
 ; CHECK: [[SLOT:%[0-9]+]]:_(p0) = G_GEP [[SP]], [[OFFSET]](s64)

test/CodeGen/AArch64/GlobalISel/translate-gep.ll

 ; NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 ; RUN: llc -mtriple=aarch64-linux-gnu -O0 -global-isel -stop-after=irtranslator -o - %s | FileCheck %s
 
 %type = type [4 x {i8, i32}]
 
 define i8*  @translate_element_size1(i64 %arg) {
 ; CHECK-LABEL: name: translate_element_size1
 ; CHECK: [[OFFSET:%[0-9]+]]:_(s64) = COPY $x0
-; CHECK: [[BASE:%[0-9]+]]:_(p0) = G_CONSTANT i64 0
+; CHECK: [[ZERO:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+; CHECK: [[BASE:%[0-9]+]]:_(p0) = G_INTTOPTR [[ZERO]]
 ; CHECK: [[GEP:%[0-9]+]]:_(p0) = G_GEP [[BASE]], [[OFFSET]]
   %tmp = getelementptr i8, i8* null, i64 %arg
   ret i8* %tmp
 }
 
 define %type* @first_offset_const(%type* %addr) {
 
   ; CHECK-LABEL: name: first_offset_const