[llvm][AsmPrinter] Extend Constant Pool Handling for UEFI

Constant pool handling must be supported for UEFI targets. Currently,
the only target that is actively worked on is UEFI x86_64 and this patch
adds a test for this target.

Author: Prabhuk

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -4096,7 +4096,8 @@ const MCExpr *AsmPrinter::lowerBlockAddressConstant(const BlockAddress &BA) {
 
 /// GetCPISymbol - Return the symbol for the specified constant pool entry.
 MCSymbol *AsmPrinter::GetCPISymbol(unsigned CPID) const {
-  if (getSubtargetInfo().getTargetTriple().isWindowsMSVCEnvironment()) {
+  if (getSubtargetInfo().getTargetTriple().isWindowsMSVCEnvironment() ||
+      getSubtargetInfo().getTargetTriple().isUEFI()) {
     const MachineConstantPoolEntry &CPE =
         MF->getConstantPool()->getConstants()[CPID];
     if (!CPE.isMachineConstantPoolEntry()) {

llvm/test/CodeGen/X86/win_cst_pool.ll

@@ -2,6 +2,8 @@
 ; RUN: llc < %s -mattr=sse2 -mattr=avx | FileCheck %s
 ; RUN: llc < %s -mtriple=x86_64-win32 -mattr=sse2 -mattr=avx | FileCheck %s
 ; RUN: llc < %s -mtriple=x86_64-windows-msvc -mattr=sse2 -mattr=avx | FileCheck %s
+; UEFI environment.
+; RUN: llc < %s -mtriple=x86_64-uefi -mattr=sse2 -mattr=avx | FileCheck %s
 ; GNU environment.
 ; RUN: llc < %s -mtriple=x86_64-win32-gnu -mattr=sse2 -mattr=avx | FileCheck -check-prefix=MINGW %s
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"