Use .set expression for x86 pic jump table reference to reduce assembly relocation. rdar://7738756

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101085 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 16 insertions, 2 deletions

diff --git a/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp b/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
index 2056e9506d..9e6cf50b6a 100644
--- a/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
+++ b/lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
@@ -169,6 +169,15 @@ MCOperand X86MCInstLower::LowerSymbolOperand(const MachineOperand &MO,
     Expr = MCBinaryExpr::CreateSub(Expr, 
                                MCSymbolRefExpr::Create(GetPICBaseSymbol(), Ctx),
                                    Ctx);
+    if (MO.isJTI() && AsmPrinter.MAI->hasSetDirective()) {
+      // If .set directive is supported, use it to reduce the number of
+      // relocations the assembler will generate for differences between
+      // local labels. This is only safe when the symbols are in the same
+      // section so we are restricting it to jumptable references.
+      MCSymbol *Label = Ctx.CreateTempSymbol();
+      AsmPrinter.OutStreamer.EmitAssignment(Label, Expr);
+      Expr = MCSymbolRefExpr::Create(Label, Ctx);
+    }
     break;
   }
   
diff --git a/test/CodeGen/X86/pic_jumptable.ll b/test/CodeGen/X86/pic_jumptable.ll
index b3750c1e8e..aad0a6171c 100644
--- a/test/CodeGen/X86/pic_jumptable.ll
+++ b/test/CodeGen/X86/pic_jumptable.ll
@@ -1,13 +1,18 @@
 ; RUN: llc < %s -relocation-model=pic -mtriple=i386-linux-gnu -asm-verbose=false | not grep -F .text
-; RUN: llc < %s -relocation-model=pic -mtriple=i686-apple-darwin -asm-verbose=false | not grep lea
-; RUN: llc < %s -relocation-model=pic -mtriple=i686-apple-darwin -asm-verbose=false | grep add | count 2
+; RUN: llc < %s -relocation-model=pic -mtriple=i686-apple-darwin -asm-verbose=false | FileCheck %s
 ; RUN: llc < %s                       -mtriple=x86_64-apple-darwin | not grep 'lJTI'
 ; rdar://6971437
+; rdar://7738756
 
 declare void @_Z3bari(i32)
 
 define linkonce void @_Z3fooILi1EEvi(i32 %Y) nounwind {
 entry:
+; CHECK:       L1$pb
+; CHECK-NOT:   leal
+; CHECK:       Ltmp0 = LJTI1_0-L1$pb
+; CHECK-NEXT:  addl Ltmp0(%eax,%ecx,4)
+; CHECK-NEXT:  jmpl *%eax
 	%Y_addr = alloca i32		; <i32*> [#uses=2]
 	%"alloca point" = bitcast i32 0 to i32		; <i32> [#uses=0]
 	store i32 %Y, i32* %Y_addr