From d9904414c214ef94c480ce1cd76ebde0558403a0 Mon Sep 17 00:00:00 2001
From: Ewan Crawford <ewan@codeplay.com>
Date: Tue, 31 Jul 2018 15:53:03 +0000
Subject: [PATCH] Fix InstCombine address space assert

Workaround bug where the InstCombine pass was asserting on the IR added in lit
test, where we have a bitcast instruction after a GEP from an addrspace cast.

The second bitcast in the test was getting combined into
`bitcast <16 x i32>* %0 to <16 x i32> addrspace(3)*`, which looks like it should
be an addrspace cast instruction instead. Otherwise if control flow is allowed
to continue as it is now we create a GEP instruction
`<badref> = getelementptr inbounds <16 x i32>, <16 x i32>* %0, i32 0`. However
because the type of this instruction doesn't match the address space we hit an
assert when replacing the bitcast with that GEP.

```
void llvm::Value::doRAUW(llvm::Value*, bool): Assertion `New->getType() == getType() && "replaceAllUses of value with new value of different type!"' failed.
```

Differential Revision: https://reviews.llvm.org/D50058


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338395 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstCombineCasts.cpp          |  6 ++++++
 test/Transforms/InstCombine/gep-addrspace.ll  | 19 +++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index e8ea7396a96..fd59c3a7c0c 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2243,6 +2243,12 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     Type *DstElTy = DstPTy->getElementType();
     Type *SrcElTy = SrcPTy->getElementType();
 
+    // Casting pointers between the same type, but with different address spaces
+    // is an addrspace cast rather than a bitcast.
+    if ((DstElTy == SrcElTy) &&
+        (DstPTy->getAddressSpace() != SrcPTy->getAddressSpace()))
+      return new AddrSpaceCastInst(Src, DestTy);
+
     // If we are casting a alloca to a pointer to a type of the same
     // size, rewrite the allocation instruction to allocate the "right" type.
     // There is no need to modify malloc calls because it is their bitcast that
diff --git a/test/Transforms/InstCombine/gep-addrspace.ll b/test/Transforms/InstCombine/gep-addrspace.ll
index 1cd1e46251d..fadf2ae6bf6 100644
--- a/test/Transforms/InstCombine/gep-addrspace.ll
+++ b/test/Transforms/InstCombine/gep-addrspace.ll
@@ -65,3 +65,22 @@ define { i8, i8 } @inbounds_after_addrspacecast() {
   ret { i8, i8 } %insert
 }
 
+
+declare spir_func <16 x i32> @my_extern_func()
+
+; check that a bitcast is not generated when we need an addrspace cast
+define void @bitcast_after_gep(<16 x i32>* %t0) {
+; CHECK-LABEL: @bitcast_after_gep(
+; CHECK-NEXT:    [[T4:%.*]] = addrspacecast <16 x i32>* [[T0:%.*]] to <16 x i32> addrspace(3)*
+; CHECK-NEXT:    [[CALL:%.*]] = call spir_func <16 x i32> @my_extern_func()
+; CHECK-NEXT:    store <16 x i32> [[CALL]], <16 x i32> addrspace(3)* [[T4]], align 64
+; CHECK-NEXT:    ret void
+;
+  %t1 = bitcast <16 x i32>* %t0 to [16 x i32]*
+  %t2 = addrspacecast [16 x i32]* %t1 to [16 x i32] addrspace(3)*
+  %t3 = getelementptr inbounds [16 x i32], [16 x i32] addrspace(3)* %t2, i64 0, i64 0
+  %t4 = bitcast i32 addrspace(3)* %t3 to <16 x i32> addrspace(3)*
+  %call = call spir_func <16 x i32> @my_extern_func()
+  store <16 x i32> %call, <16 x i32> addrspace(3)* %t4
+  ret void
+}
-- 
2.40.0