X86: Produce @ABS8 symbol modifiers for absolute symbols in range [0,128).
Differential Revision: https://reviews.llvm.org/D28689
llvm-svn: 293844
diff --git a/llvm/lib/Target/X86/X86Subtarget.cpp b/llvm/lib/Target/X86/X86Subtarget.cpp
index 586bb7b..69ed9256 100644
--- a/llvm/lib/Target/X86/X86Subtarget.cpp
+++ b/llvm/lib/Target/X86/X86Subtarget.cpp
@@ -15,6 +15,7 @@
#include "X86InstrInfo.h"
#include "X86TargetMachine.h"
#include "llvm/IR/Attributes.h"
+#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/Support/CommandLine.h"
@@ -93,8 +94,17 @@
return X86II::MO_NO_FLAG;
// Absolute symbols can be referenced directly.
- if (GV && GV->isAbsoluteSymbolRef())
- return X86II::MO_NO_FLAG;
+ if (GV) {
+ if (Optional<ConstantRange> CR = GV->getAbsoluteSymbolRange()) {
+ // See if we can use the 8-bit immediate form. Note that some instructions
+ // will sign extend the immediate operand, so to be conservative we only
+ // accept the range [0,128).
+ if (CR->getUnsignedMax().ult(128))
+ return X86II::MO_ABS8;
+ else
+ return X86II::MO_NO_FLAG;
+ }
+ }
if (TM.shouldAssumeDSOLocal(M, GV))
return classifyLocalReference(GV);