[X86] Teach -Os immediate sharing code to not count constant uses that will become INC/DEC.

INC/DEC don't use an immediate so we don't need to count it. We
also shouldn't use the custom isel for it.

Fixes PR42998.

llvm-svn: 369863

2 files changed, 21 insertions, 22 deletions

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 46886419421..e0a462471a7 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -362,6 +362,11 @@ namespace {
         if (User->getNumOperands() != 2)
           continue;
 
+        // If this can match to INC/DEC, don't count it as a use.
+        if (User->getOpcode() == ISD::ADD &&
+            (isOneConstant(SDValue(N, 0)) || isAllOnesConstant(SDValue(N, 0))))
+          continue;
+
         // Immediates that are used for offsets as part of stack
         // manipulation should be left alone. These are typically
         // used to indicate SP offsets for argument passing and
@@ -4369,6 +4374,10 @@ void X86DAGToDAGISel::Select(SDNode *Node) {
     if (!isInt<8>(Val) && !isInt<32>(Val))
       break;
 
+    // If this can match to INC/DEC, let it go.
+    if (Opcode == ISD::ADD && (Val == 1 || Val == -1))
+      break;
+
     // Check if we should avoid folding this immediate.
     if (!shouldAvoidImmediateInstFormsForSize(N1.getNode()))
       break;
diff --git a/llvm/test/CodeGen/X86/pr42998.ll b/llvm/test/CodeGen/X86/pr42998.ll
index 6d67417286a..e3d6a560a11 100644
--- a/llvm/test/CodeGen/X86/pr42998.ll
+++ b/llvm/test/CodeGen/X86/pr42998.ll
@@ -5,12 +5,11 @@
 define i64 @imm1_Oz(i32 %x, i32 %y) minsize nounwind {
 ; CHECK-LABEL: imm1_Oz:
 ; CHECK:       # %bb.0:
+; CHECK-NEXT:    # kill: def $esi killed $esi def $rsi
 ; CHECK-NEXT:    # kill: def $edi killed $edi def $rdi
-; CHECK-NEXT:    pushq $1
-; CHECK-NEXT:    popq %rax
-; CHECK-NEXT:    leal (%rdi,%rax), %ecx
-; CHECK-NEXT:    addl %esi, %eax
-; CHECK-NEXT:    addq %rcx, %rax
+; CHECK-NEXT:    leal 1(%rdi), %eax
+; CHECK-NEXT:    incl %esi
+; CHECK-NEXT:    addq %rsi, %rax
 ; CHECK-NEXT:    retq
   %x1 = add i32 %x, 1
   %y1 = add i32 %y, 1
@@ -21,23 +20,14 @@ define i64 @imm1_Oz(i32 %x, i32 %y) minsize nounwind {
 }
 
 define i64 @imm1_Os(i32 %x, i32 %y) optsize nounwind {
-; FAST-INCDEC-LABEL: imm1_Os:
-; FAST-INCDEC:       # %bb.0:
-; FAST-INCDEC-NEXT:    # kill: def $edi killed $edi def $rdi
-; FAST-INCDEC-NEXT:    movl $1, %eax
-; FAST-INCDEC-NEXT:    leal (%rdi,%rax), %ecx
-; FAST-INCDEC-NEXT:    addl %esi, %eax
-; FAST-INCDEC-NEXT:    addq %rcx, %rax
-; FAST-INCDEC-NEXT:    retq
-;
-; SLOW-INCDEC-LABEL: imm1_Os:
-; SLOW-INCDEC:       # %bb.0:
-; SLOW-INCDEC-NEXT:    movl $1, %eax
-; SLOW-INCDEC-NEXT:    # kill: def $edi killed $edi def $rdi
-; SLOW-INCDEC-NEXT:    leal (%rdi,%rax), %ecx
-; SLOW-INCDEC-NEXT:    addl %esi, %eax
-; SLOW-INCDEC-NEXT:    addq %rcx, %rax
-; SLOW-INCDEC-NEXT:    retq
+; CHECK-LABEL: imm1_Os:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    # kill: def $esi killed $esi def $rsi
+; CHECK-NEXT:    # kill: def $edi killed $edi def $rdi
+; CHECK-NEXT:    leal 1(%rdi), %eax
+; CHECK-NEXT:    incl %esi
+; CHECK-NEXT:    addq %rsi, %rax
+; CHECK-NEXT:    retq
   %x1 = add i32 %x, 1
   %y1 = add i32 %y, 1
   %x1z = zext i32 %x1 to i64