[PATCH] D41114: Look through address space casts in IsConstantOffsetFromGlobal()

[Alexander Richardson via Phabricator via llvm-commits]

arichardson created this revision.
arichardson added reviewers: lattner, arsenm, mehdi_amini.
Herald added a subscriber: wdng.

I originally needed this change for our fork of clang targeting CHERI which
uses address space 200 extensively. It turns out the only test that fails
after this change is Transforms/ConstProp/loads.ll which already contains
a FIXME for this case.


https://reviews.llvm.org/D41114

Files:
  lib/Analysis/ConstantFolding.cpp
  test/Transforms/ConstProp/loads.ll


Index: test/Transforms/ConstProp/loads.ll
===================================================================
--- test/Transforms/ConstProp/loads.ll
+++ test/Transforms/ConstProp/loads.ll
@@ -40,16 +40,13 @@
   %r = load i16, i16 addrspace(1)* addrspacecast(i32* getelementptr ({{i32,i8},i32}, {{i32,i8},i32}* @g1, i32 0, i32 0, i32 0) to i16 addrspace(1)*)
   ret i16 %r
 
-; FIXME: Should be able to load through a constant addrspacecast.
 ; 0xBEEF
 ; LE-LABEL: @test2_addrspacecast(
-; XLE: ret i16 -16657
-; LE: load i16, i16 addrspace(1)* addrspacecast
+; LE: ret i16 -16657
 
 ; 0xDEAD
 ; BE-LABEL: @test2_addrspacecast(
-; XBE: ret i16 -8531
-; BE: load i16, i16 addrspace(1)* addrspacecast
+; BE: ret i16 -8531
 }
 
 ; Load of second 16 bits of 32-bit value.
Index: lib/Analysis/ConstantFolding.cpp
===================================================================
--- lib/Analysis/ConstantFolding.cpp
+++ lib/Analysis/ConstantFolding.cpp
@@ -295,9 +295,10 @@
   auto *CE = dyn_cast<ConstantExpr>(C);
   if (!CE) return false;
 
-  // Look through ptr->int and ptr->ptr casts.
+  // Look through ptr->int, ptr->ptr casts and address space casts.
   if (CE->getOpcode() == Instruction::PtrToInt ||
-      CE->getOpcode() == Instruction::BitCast)
+      CE->getOpcode() == Instruction::BitCast ||
+      CE->getOpcode() == Instruction::AddrSpaceCast)
     return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, DL);
 
   // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)


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