[X86] Don't transform atomic-load-add into an inc/dec when inc/dec is slow

llvm-svn: 219357

2 files changed, 21 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 7665beaa2d0..c42a05f46ba 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1706,7 +1706,8 @@ static const uint16_t AtomicOpcTbl[AtomicOpcEnd][AtomicSzEnd] = {
 static SDValue getAtomicLoadArithTargetConstant(SelectionDAG *CurDAG,
                                                 SDLoc dl,
                                                 enum AtomicOpc &Op, MVT NVT,
-                                                SDValue Val) {
+                                                SDValue Val,
+                                                const X86Subtarget *Subtarget) {
   if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Val)) {
     int64_t CNVal = CN->getSExtValue();
     // Quit if not 32-bit imm.
@@ -1721,7 +1722,7 @@ static SDValue getAtomicLoadArithTargetConstant(SelectionDAG *CurDAG,
     // For atomic-load-add, we could do some optimizations.
     if (Op == ADD) {
       // Translate to INC/DEC if ADD by 1 or -1.
-      if ((CNVal == 1) || (CNVal == -1)) {
+      if (((CNVal == 1) || (CNVal == -1)) && !Subtarget->slowIncDec()) {
         Op = (CNVal == 1) ? INC : DEC;
         // No more constant operand after being translated into INC/DEC.
         return SDValue();
@@ -1793,7 +1794,7 @@ SDNode *X86DAGToDAGISel::SelectAtomicLoadArith(SDNode *Node, MVT NVT) {
       break;
   }
 
-  Val = getAtomicLoadArithTargetConstant(CurDAG, dl, Op, NVT, Val);
+  Val = getAtomicLoadArithTargetConstant(CurDAG, dl, Op, NVT, Val, Subtarget);
   bool isUnOp = !Val.getNode();
   bool isCN = Val.getNode() && (Val.getOpcode() == ISD::TargetConstant);
 
diff --git a/llvm/test/CodeGen/X86/atomic_add.ll b/llvm/test/CodeGen/X86/atomic_add.ll
index bdd25e6a2a5..f60212de533 100644
--- a/llvm/test/CodeGen/X86/atomic_add.ll
+++ b/llvm/test/CodeGen/X86/atomic_add.ll
@@ -1,4 +1,5 @@
 ; RUN: llc < %s -march=x86-64 -verify-machineinstrs | FileCheck %s
+; RUN: llc < %s -march=x86-64 -mattr=slow-incdec -verify-machineinstrs | FileCheck %s --check-prefix SLOW_INC
 
 ; rdar://7103704
 
@@ -14,6 +15,8 @@ define void @inc4(i64* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: inc4:
 ; CHECK: incq
+; SLOW_INC-LABEL: inc4:
+; SLOW_INC-NOT: incq
   %0 = atomicrmw add i64* %p, i64 1 monotonic
   ret void
 }
@@ -39,6 +42,8 @@ define void @inc3(i8* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: inc3:
 ; CHECK: incb
+; SLOW_INC-LABEL: inc3:
+; SLOW_INC-NOT: incb
   %0 = atomicrmw add i8* %p, i8 1 monotonic
   ret void
 }
@@ -64,6 +69,8 @@ define void @inc2(i16* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: inc2:
 ; CHECK: incw
+; SLOW_INC-LABEL: inc2:
+; SLOW_INC-NOT: incw
   %0 = atomicrmw add i16* %p, i16 1 monotonic
   ret void
 }
@@ -89,6 +96,8 @@ define void @inc1(i32* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: inc1:
 ; CHECK: incl
+; SLOW_INC-LABEL: inc1:
+; SLOW_INC-NOT: incl
   %0 = atomicrmw add i32* %p, i32 1 monotonic
   ret void
 }
@@ -113,6 +122,8 @@ define void @dec4(i64* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: dec4:
 ; CHECK: decq
+; SLOW_INC-LABEL: dec4:
+; SLOW_INC-NOT: decq
   %0 = atomicrmw sub i64* %p, i64 1 monotonic
   ret void
 }
@@ -138,6 +149,8 @@ define void @dec3(i8* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: dec3:
 ; CHECK: decb
+; SLOW_INC-LABEL: dec3:
+; SLOW_INC-NOT: decb
   %0 = atomicrmw sub i8* %p, i8 1 monotonic
   ret void
 }
@@ -163,6 +176,8 @@ define void @dec2(i16* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: dec2:
 ; CHECK: decw
+; SLOW_INC-LABEL: dec2:
+; SLOW_INC-NOT: decw
   %0 = atomicrmw sub i16* %p, i16 1 monotonic
   ret void
 }
@@ -189,6 +204,8 @@ define void @dec1(i32* nocapture %p) nounwind ssp {
 entry:
 ; CHECK-LABEL: dec1:
 ; CHECK: decl
+; SLOW_INC-LABEL: dec1:
+; SLOW_INC-NOT: decl
   %0 = atomicrmw sub i32* %p, i32 1 monotonic
   ret void
 }