4 files changed, 32 insertions, 14 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5d7890ee08f..c61b24f8d21 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3037,6 +3037,14 @@ SDValue DAGCombiner::visitSUBO(SDNode *N) {
     return CombineTo(N, DAG.getConstant(0, DL, VT),
                      DAG.getConstant(0, DL, CarryVT));
 
+  ConstantSDNode *N1C = getAsNonOpaqueConstant(N1);
+
+  // fold (subox, c) -> (addo x, -c)
+  if (IsSigned && N1C && !N1C->getAPIntValue().isMinSignedValue()) {
+    return DAG.getNode(ISD::SADDO, DL, N->getVTList(), N0,
+                       DAG.getConstant(-N1C->getAPIntValue(), DL, VT));
+  }
+
   // fold (subo x, 0) -> x + no borrow
   if (isNullOrNullSplat(N1))
     return CombineTo(N, N0, DAG.getConstant(0, DL, CarryVT));
diff --git a/llvm/test/CodeGen/SystemZ/int-ssub-07.ll b/llvm/test/CodeGen/SystemZ/int-ssub-07.ll
index dd3b00a4bb0..970c14e0391 100644
--- a/llvm/test/CodeGen/SystemZ/int-ssub-07.ll
+++ b/llvm/test/CodeGen/SystemZ/int-ssub-07.ll
@@ -154,9 +154,9 @@ define zeroext i1 @f9(i64 %dummy, i64 %a, i64 *%res) {
 ; Check the next value down, which must use register subtraction instead.
 define zeroext i1 @f10(i64 %dummy, i64 %a, i64 *%res) {
 ; CHECK-LABEL: f10:
-; CHECK: lgfi [[REG1:%r[0-9]+]], -2147483648
-; CHECK: sgr %r3, [[REG1]]
-; CHECK-DAG: stg %r3, 0(%r4)
+; CHECK: llilh [[REG1:%r[0-9]+]], 32768
+; CHECK: agr [[REG1]], %r3
+; CHECK-DAG: stg [[REG1]], 0(%r4)
 ; CHECK-DAG: ipm [[REG:%r[0-5]]]
 ; CHECK-DAG: afi [[REG]], 1342177280
 ; CHECK-DAG: risbg %r2, [[REG]], 63, 191, 33
diff --git a/llvm/test/CodeGen/X86/sub-with-overflow.ll b/llvm/test/CodeGen/X86/sub-with-overflow.ll
index 0bcf2d8a565..6de0beeabdf 100644
--- a/llvm/test/CodeGen/X86/sub-with-overflow.ll
+++ b/llvm/test/CodeGen/X86/sub-with-overflow.ll
@@ -83,7 +83,8 @@ declare {i32, i1} @llvm.usub.with.overflow.i32(i32, i32)
 define i1 @func3(i32 %x) nounwind {
 ; CHECK-LABEL: func3:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    cmpl $1, {{[0-9]+}}(%esp)
+; CHECK-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; CHECK-NEXT:    decl %eax
 ; CHECK-NEXT:    seto %al
 ; CHECK-NEXT:    retl
 entry:
diff --git a/llvm/test/CodeGen/X86/xaluo.ll b/llvm/test/CodeGen/X86/xaluo.ll
index 70d36fd7fa1..0de8bdeddd6 100644
--- a/llvm/test/CodeGen/X86/xaluo.ll
+++ b/llvm/test/CodeGen/X86/xaluo.ll
@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -mtriple=x86_64-darwin-unknown < %s | FileCheck %s --check-prefix=SDAG
+; RUN: llc -mtriple=x86_64-darwin-unknown < %s | FileCheck %s --check-prefix=SDAG --check-prefix=GENERIC
 ; RUN: llc -mtriple=x86_64-darwin-unknown -fast-isel -fast-isel-abort=1 < %s | FileCheck %s --check-prefix=FAST
-; RUN: llc -mtriple=x86_64-darwin-unknown -mcpu=knl < %s | FileCheck %s --check-prefix=SDAG
+; RUN: llc -mtriple=x86_64-darwin-unknown -mcpu=knl < %s | FileCheck %s --check-prefix=SDAG --check-prefix=KNL
 
 ;
 ; Get the actual value of the overflow bit.
@@ -1104,14 +1104,14 @@ define i32 @incovfselectstore(i32 %v1, i32 %v2, i32* %x) {
 
 ; Make sure we select a DEC for both the data use and the flag use.
 define i32 @decovfselectstore(i32 %v1, i32 %v2, i32* %x) {
-; SDAG-LABEL: decovfselectstore:
-; SDAG:       ## %bb.0:
-; SDAG-NEXT:    movl %esi, %eax
-; SDAG-NEXT:    movl %edi, %ecx
-; SDAG-NEXT:    decl %ecx
-; SDAG-NEXT:    cmovol %edi, %eax
-; SDAG-NEXT:    movl %ecx, (%rdx)
-; SDAG-NEXT:    retq
+; GENERIC-LABEL: decovfselectstore:
+; GENERIC:       ## %bb.0:
+; GENERIC-NEXT:    movl %esi, %eax
+; GENERIC-NEXT:    movl %edi, %ecx
+; GENERIC-NEXT:    decl %ecx
+; GENERIC-NEXT:    cmovol %edi, %eax
+; GENERIC-NEXT:    movl %ecx, (%rdx)
+; GENERIC-NEXT:    retq
 ;
 ; FAST-LABEL: decovfselectstore:
 ; FAST:       ## %bb.0:
@@ -1121,6 +1121,15 @@ define i32 @decovfselectstore(i32 %v1, i32 %v2, i32* %x) {
 ; FAST-NEXT:    cmovol %edi, %eax
 ; FAST-NEXT:    movl %ecx, (%rdx)
 ; FAST-NEXT:    retq
+;
+; KNL-LABEL: decovfselectstore:
+; KNL:       ## %bb.0:
+; KNL-NEXT:    movl %esi, %eax
+; KNL-NEXT:    movl %edi, %ecx
+; KNL-NEXT:    addl $-1, %ecx
+; KNL-NEXT:    cmovol %edi, %eax
+; KNL-NEXT:    movl %ecx, (%rdx)
+; KNL-NEXT:    retq
   %t = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %v1, i32 1)
   %obit = extractvalue {i32, i1} %t, 1
   %ret = select i1 %obit, i32 %v1, i32 %v2