[llvm] r297404 - [DAGCombiner] Do various combine on usubo.
Amaury Sechet via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 9 11:28:00 PST 2017
Author: deadalnix
Date: Thu Mar 9 13:28:00 2017
New Revision: 297404
URL: http://llvm.org/viewvc/llvm-project?rev=297404&view=rev
Log:
[DAGCombiner] Do various combine on usubo.
Summary: This essentially does the same transform as for SUBC.
Reviewers: jyknight, nemanjai, mkuper, spatel, RKSimon, zvi, bkramer
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D30437
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/trunk/test/CodeGen/X86/xaluo.ll
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=297404&r1=297403&r2=297404&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Mar 9 13:28:00 2017
@@ -236,6 +236,7 @@ namespace {
SDValue visitSUB(SDNode *N);
SDValue visitADDC(SDNode *N);
SDValue visitSUBC(SDNode *N);
+ SDValue visitUSUBO(SDNode *N);
SDValue visitADDE(SDNode *N);
SDValue visitSUBE(SDNode *N);
SDValue visitMUL(SDNode *N);
@@ -1400,6 +1401,7 @@ SDValue DAGCombiner::visit(SDNode *N) {
case ISD::SUB: return visitSUB(N);
case ISD::ADDC: return visitADDC(N);
case ISD::SUBC: return visitSUBC(N);
+ case ISD::USUBO: return visitUSUBO(N);
case ISD::ADDE: return visitADDE(N);
case ISD::SUBE: return visitSUBE(N);
case ISD::MUL: return visitMUL(N);
@@ -2132,6 +2134,38 @@ SDValue DAGCombiner::visitSUBC(SDNode *N
return SDValue();
}
+
+SDValue DAGCombiner::visitUSUBO(SDNode *N) {
+ SDValue N0 = N->getOperand(0);
+ SDValue N1 = N->getOperand(1);
+ EVT VT = N0.getValueType();
+ if (VT.isVector())
+ return SDValue();
+
+ EVT CarryVT = N->getValueType(1);
+ SDLoc DL(N);
+
+ // If the flag result is dead, turn this into an SUB.
+ if (!N->hasAnyUseOfValue(1))
+ return CombineTo(N, DAG.getNode(ISD::SUB, DL, VT, N0, N1),
+ DAG.getUNDEF(CarryVT));
+
+ // fold (usubo x, x) -> 0 + no borrow
+ if (N0 == N1)
+ return CombineTo(N, DAG.getConstant(0, DL, VT),
+ DAG.getConstant(0, DL, CarryVT));
+
+ // fold (usubo x, 0) -> x + no borrow
+ if (isNullConstant(N1))
+ return CombineTo(N, N0, DAG.getConstant(0, DL, CarryVT));
+
+ // Canonicalize (usubo -1, x) -> ~x, i.e. (xor x, -1) + no borrow
+ if (isAllOnesConstant(N0))
+ return CombineTo(N, DAG.getNode(ISD::XOR, DL, VT, N1, N0),
+ DAG.getConstant(0, DL, CarryVT));
+
+ return SDValue();
+}
SDValue DAGCombiner::visitSUBE(SDNode *N) {
SDValue N0 = N->getOperand(0);
Modified: llvm/trunk/test/CodeGen/X86/xaluo.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/xaluo.ll?rev=297404&r1=297403&r2=297404&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/xaluo.ll (original)
+++ llvm/trunk/test/CodeGen/X86/xaluo.ll Thu Mar 9 13:28:00 2017
@@ -1372,43 +1372,23 @@ define {i64, i1} @uaddoovf(i64 %a, i64 %
define {i64, i1} @usuboovf(i64 %a, i64 %b) {
; SDAG-LABEL: usuboovf:
; SDAG: ## BB#0:
-; SDAG-NEXT: subq %rdi, %rdi
-; SDAG-NEXT: sbbb %r8b, %r8b
-; SDAG-NEXT: movq $-1, %rax
-; SDAG-NEXT: subq %rsi, %rax
-; SDAG-NEXT: sbbb %cl, %cl
-; SDAG-NEXT: subq %rdi, %rax
-; SDAG-NEXT: sbbb %dl, %dl
-; SDAG-NEXT: orb %cl, %dl
-; SDAG-NEXT: orb %r8b, %dl
-; SDAG-NEXT: andb $1, %dl
+; SDAG-NEXT: notq %rsi
+; SDAG-NEXT: xorl %edx, %edx
+; SDAG-NEXT: movq %rsi, %rax
; SDAG-NEXT: retq
;
; FAST-LABEL: usuboovf:
; FAST: ## BB#0:
-; FAST-NEXT: subq %rdi, %rdi
-; FAST-NEXT: sbbb %r8b, %r8b
-; FAST-NEXT: movq $-1, %rax
-; FAST-NEXT: subq %rsi, %rax
-; FAST-NEXT: sbbb %cl, %cl
-; FAST-NEXT: subq %rdi, %rax
-; FAST-NEXT: sbbb %dl, %dl
-; FAST-NEXT: orb %cl, %dl
-; FAST-NEXT: orb %r8b, %dl
-; FAST-NEXT: andb $1, %dl
+; FAST-NEXT: notq %rsi
+; FAST-NEXT: xorl %edx, %edx
+; FAST-NEXT: movq %rsi, %rax
; FAST-NEXT: retq
;
; KNL-LABEL: usuboovf:
; KNL: ## BB#0:
-; KNL-NEXT: subq %rdi, %rdi
-; KNL-NEXT: sbbb %dl, %dl
-; KNL-NEXT: movq $-1, %rax
-; KNL-NEXT: subq %rsi, %rax
-; KNL-NEXT: sbbb %cl, %cl
-; KNL-NEXT: orb %dl, %cl
-; KNL-NEXT: subq %rdi, %rax
-; KNL-NEXT: sbbb %dl, %dl
-; KNL-NEXT: orb %cl, %dl
+; KNL-NEXT: notq %rsi
+; KNL-NEXT: xorl %edx, %edx
+; KNL-NEXT: movq %rsi, %rax
; KNL-NEXT: retq
%t0 = call {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %a)
%v0 = extractvalue {i64, i1} %t0, 0
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