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[DAGCombine] ((c1-A)-c2) -> ((c1-c2)-A) constant-fold 

Summary: https://rise4fun.com/Alive/B0A

Reviewers: t.p.northover, RKSimon, spatel, craig.topper

Reviewed By: RKSimon

Subscribers: javed.absar, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62691

llvm-svn: 362135
This commit is contained in:
Roman Lebedev 2019-05-30 19:27:51 +00:00
parent 691b5e2ecc
commit 7eb8b5b5dd
3 changed files with 31 additions and 29 deletions
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10
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -2895,6 +2895,16 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
return DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), NewC);
}
// fold (c1-A)-c2 -> (c1-c2)-A
if (N0.getOpcode() == ISD::SUB &&
isConstantOrConstantVector(N1, /* NoOpaques */ true) &&
isConstantOrConstantVector(N0.getOperand(0), /* NoOpaques */ true)) {
SDValue NewC = DAG.FoldConstantArithmetic(
ISD::SUB, DL, VT, N0.getOperand(0).getNode(), N1.getNode());
assert(NewC && "Constant folding failed");
return DAG.getNode(ISD::SUB, DL, VT, NewC, N0.getOperand(1));
}
// fold ((A+(B+or-C))-B) -> A+or-C
if (N0.getOpcode() == ISD::ADD &&
(N0.getOperand(1).getOpcode() == ISD::SUB ||

13
llvm/test/CodeGen/AArch64/addsub-constant-folding.ll
View File

@ -344,10 +344,8 @@ define <4 x i32> @const_sub_add_const_nonsplat(<4 x i32> %arg) {
define <4 x i32> @const_sub_sub_const(<4 x i32> %arg) {
; CHECK-LABEL: const_sub_sub_const:
; CHECK: // %bb.0:
; CHECK-NEXT: movi v1.4s, #8
; CHECK-NEXT: movi v1.4s, #6
; CHECK-NEXT: sub v0.4s, v1.4s, v0.4s
; CHECK-NEXT: movi v1.4s, #2
; CHECK-NEXT: sub v0.4s, v0.4s, v1.4s
; CHECK-NEXT: ret
%t0 = sub <4 x i32> <i32 8, i32 8, i32 8, i32 8>, %arg
%t1 = sub <4 x i32> %t0, <i32 2, i32 2, i32 2, i32 2>
@ -362,13 +360,13 @@ define <4 x i32> @const_sub_sub_const_extrause(<4 x i32> %arg) {
; CHECK-NEXT: .cfi_def_cfa_offset 32
; CHECK-NEXT: .cfi_offset w30, -16
; CHECK-NEXT: movi v1.4s, #8
; CHECK-NEXT: sub v0.4s, v1.4s, v0.4s
; CHECK-NEXT: str q0, [sp] // 16-byte Folded Spill
; CHECK-NEXT: sub v0.4s, v1.4s, v0.4s
; CHECK-NEXT: bl use
; CHECK-NEXT: ldr q1, [sp] // 16-byte Folded Reload
; CHECK-NEXT: ldr x30, [sp, #16] // 8-byte Folded Reload
; CHECK-NEXT: movi v0.4s, #2
; CHECK-NEXT: sub v0.4s, v1.4s, v0.4s
; CHECK-NEXT: movi v0.4s, #6
; CHECK-NEXT: sub v0.4s, v0.4s, v1.4s
; CHECK-NEXT: add sp, sp, #32 // =32
; CHECK-NEXT: ret
%t0 = sub <4 x i32> <i32 8, i32 8, i32 8, i32 8>, %arg
@ -382,10 +380,7 @@ define <4 x i32> @const_sub_sub_const_nonsplat(<4 x i32> %arg) {
; CHECK: // %bb.0:
; CHECK-NEXT: adrp x8, .LCPI23_0
; CHECK-NEXT: ldr q1, [x8, :lo12:.LCPI23_0]
; CHECK-NEXT: adrp x8, .LCPI23_1
; CHECK-NEXT: ldr q2, [x8, :lo12:.LCPI23_1]
; CHECK-NEXT: sub v0.4s, v1.4s, v0.4s
; CHECK-NEXT: sub v0.4s, v0.4s, v2.4s
; CHECK-NEXT: ret
%t0 = sub <4 x i32> <i32 21, i32 undef, i32 8, i32 8>, %arg
%t1 = sub <4 x i32> %t0, <i32 2, i32 3, i32 undef, i32 2>

37
llvm/test/CodeGen/X86/addsub-constant-folding.ll
View File

@ -500,17 +500,15 @@ define <4 x i32> @const_sub_add_const_nonsplat(<4 x i32> %arg) {
define <4 x i32> @const_sub_sub_const(<4 x i32> %arg) {
; X86-LABEL: const_sub_sub_const:
; X86: # %bb.0:
; X86-NEXT: movdqa {{.*#+}} xmm1 = [8,8,8,8]
; X86-NEXT: movdqa {{.*#+}} xmm1 = [6,6,6,6]
; X86-NEXT: psubd %xmm0, %xmm1
; X86-NEXT: psubd {{\.LCPI.*}}, %xmm1
; X86-NEXT: movdqa %xmm1, %xmm0
; X86-NEXT: retl
;
; X64-LABEL: const_sub_sub_const:
; X64: # %bb.0:
; X64-NEXT: movdqa {{.*#+}} xmm1 = [8,8,8,8]
; X64-NEXT: movdqa {{.*#+}} xmm1 = [6,6,6,6]
; X64-NEXT: psubd %xmm0, %xmm1
; X64-NEXT: psubd {{.*}}(%rip), %xmm1
; X64-NEXT: movdqa %xmm1, %xmm0
; X64-NEXT: retq
%t0 = sub <4 x i32> <i32 8, i32 8, i32 8, i32 8>, %arg
@ -523,13 +521,14 @@ define <4 x i32> @const_sub_sub_const_extrause(<4 x i32> %arg) {
; X86: # %bb.0:
; X86-NEXT: subl $28, %esp
; X86-NEXT: .cfi_def_cfa_offset 32
; X86-NEXT: movdqa {{.*#+}} xmm1 = [8,8,8,8]
; X86-NEXT: psubd %xmm0, %xmm1
; X86-NEXT: movdqu %xmm1, (%esp) # 16-byte Spill
; X86-NEXT: movdqa %xmm1, %xmm0
; X86-NEXT: movdqa %xmm0, %xmm1
; X86-NEXT: movdqu %xmm0, (%esp) # 16-byte Spill
; X86-NEXT: movdqa {{.*#+}} xmm0 = [8,8,8,8]
; X86-NEXT: psubd %xmm1, %xmm0
; X86-NEXT: calll use
; X86-NEXT: movdqu (%esp), %xmm0 # 16-byte Reload
; X86-NEXT: psubd {{\.LCPI.*}}, %xmm0
; X86-NEXT: movdqa {{.*#+}} xmm0 = [6,6,6,6]
; X86-NEXT: movdqu (%esp), %xmm1 # 16-byte Reload
; X86-NEXT: psubd %xmm1, %xmm0
; X86-NEXT: addl $28, %esp
; X86-NEXT: .cfi_def_cfa_offset 4
; X86-NEXT: retl
@ -538,13 +537,13 @@ define <4 x i32> @const_sub_sub_const_extrause(<4 x i32> %arg) {
; X64: # %bb.0:
; X64-NEXT: subq $24, %rsp
; X64-NEXT: .cfi_def_cfa_offset 32
; X64-NEXT: movdqa {{.*#+}} xmm1 = [8,8,8,8]
; X64-NEXT: psubd %xmm0, %xmm1
; X64-NEXT: movdqa %xmm1, (%rsp) # 16-byte Spill
; X64-NEXT: movdqa %xmm1, %xmm0
; X64-NEXT: movdqa %xmm0, %xmm1
; X64-NEXT: movdqa %xmm0, (%rsp) # 16-byte Spill
; X64-NEXT: movdqa {{.*#+}} xmm0 = [8,8,8,8]
; X64-NEXT: psubd %xmm1, %xmm0
; X64-NEXT: callq use
; X64-NEXT: movdqa (%rsp), %xmm0 # 16-byte Reload
; X64-NEXT: psubd {{.*}}(%rip), %xmm0
; X64-NEXT: movdqa {{.*#+}} xmm0 = [6,6,6,6]
; X64-NEXT: psubd (%rsp), %xmm0 # 16-byte Folded Reload
; X64-NEXT: addq $24, %rsp
; X64-NEXT: .cfi_def_cfa_offset 8
; X64-NEXT: retq
@ -557,17 +556,15 @@ define <4 x i32> @const_sub_sub_const_extrause(<4 x i32> %arg) {
define <4 x i32> @const_sub_sub_const_nonsplat(<4 x i32> %arg) {
; X86-LABEL: const_sub_sub_const_nonsplat:
; X86: # %bb.0:
; X86-NEXT: movdqa {{.*#+}} xmm1 = <21,u,8,8>
; X86-NEXT: movdqa {{.*#+}} xmm1 = <19,u,u,6>
; X86-NEXT: psubd %xmm0, %xmm1
; X86-NEXT: psubd {{\.LCPI.*}}, %xmm1
; X86-NEXT: movdqa %xmm1, %xmm0
; X86-NEXT: retl
;
; X64-LABEL: const_sub_sub_const_nonsplat:
; X64: # %bb.0:
; X64-NEXT: movdqa {{.*#+}} xmm1 = <21,u,8,8>
; X64-NEXT: movdqa {{.*#+}} xmm1 = <19,u,u,6>
; X64-NEXT: psubd %xmm0, %xmm1
; X64-NEXT: psubd {{.*}}(%rip), %xmm1
; X64-NEXT: movdqa %xmm1, %xmm0
; X64-NEXT: retq
%t0 = sub <4 x i32> <i32 21, i32 undef, i32 8, i32 8>, %arg