[clang] [lld] [llvm] [WIP][IR][Constants] Change the semantic of `ConstantPointerNull` to represent an actual `nullptr` instead of a zero-value pointer (PR #166667)

[Alexander Richardson via llvm-commits]

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@@ -22,7 +22,7 @@ define i8 @test_load8(ptr %a) sanitize_hwaddress {
 ; CHECK-LABEL: define i8 @test_load8
 ; CHECK-SAME: (ptr [[A:%.*]]) #[[ATTR0:[0-9]+]] {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[DOTHWASAN_SHADOW:%.*]] = call ptr asm "", "=r,0"(ptr null)
+; CHECK-NEXT:    [[DOTHWASAN_SHADOW:%.*]] = call ptr asm "", "=r,0"(ptr zeroinitializer)
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arichardson wrote:

Where is this `ptr inttoptr 0` coming from? Shouldn't it be using `ConstantPointerNull`? That would reduce the diff quite a lot.

https://github.com/llvm/llvm-project/pull/166667