Re-Reland [X86] Respect code models more when determining if a global reference can fit in 32 bits (#75386)

For non-GlobalValue references, the small and medium code models can use
32 bit constants.

For GlobalValue references, use TargetMachine::isLargeGlobalObject().
Look through aliases for determining if a GlobalValue is small or large.
Even the large code model can reference small objects with 32 bit
constants as long as we're in no-pic mode, or if the reference is offset
from the GOT.

Original commit broke the build...

First reland broke large PIC builds referencing small data since it was using GOTOFF as a 32-bit constant.

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index 5428e14..3f96bd3 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -39,10 +39,16 @@ TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
 
 TargetMachine::~TargetMachine() = default;
 
-bool TargetMachine::isLargeGlobalObject(const GlobalObject *GO) const {
+bool TargetMachine::isLargeGlobalValue(const GlobalValue *GVal) const {
   if (getTargetTriple().getArch() != Triple::x86_64)
     return false;
 
+  auto *GO = GVal->getAliaseeObject();
+
+  // Be conservative if we can't find an underlying GlobalObject.
+  if (!GO)
+    return true;
+
   auto *GV = dyn_cast<GlobalVariable>(GO);
 
   // Functions/GlobalIFuncs are only large under the large code model.