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[DAGCombiner] add missing folds for scalar select of {-1,0,1} 

The motivation for filling out these select-of-constants cases goes back to D24480, 
where we discussed removing an IR fold from add(zext) --> select. And that goes back to:
https://reviews.llvm.org/rL75531
https://reviews.llvm.org/rL159230

The idea is that we should always canonicalize patterns like this to a select-of-constants 
in IR because that's the smallest IR and the best for value tracking. Note that we currently 
do the opposite in some cases (like the cases in *this* patch). Ie, the proposed folds in 
this patch already exist in InstCombine today:
https://github.com/llvm-mirror/llvm/blob/master/lib/Transforms/InstCombine/InstCombineSelect.cpp#L1151

As this patch shows, most targets generate better machine code for simple ext/add/not ops 
rather than a select of constants. So the follow-up steps to make this less of a patchwork 
of special-case folds and missing IR canonicalization:

1. Have DAGCombiner convert any select of constants into ext/add/not ops.
2  Have InstCombine canonicalize in the other direction (create more selects).

Differential Revision: https://reviews.llvm.org/D30180

llvm-svn: 296137
This commit is contained in:
Sanjay Patel 2017-02-24 17:17:33 +00:00
parent 4987856fbc
commit 832b1622d8
8 changed files with 72 additions and 112 deletions
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35
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -5599,8 +5599,13 @@ SDValue DAGCombiner::foldSelectOfConstants(SDNode *N) {
if (!isa<ConstantSDNode>(N1) || !isa<ConstantSDNode>(N2))
return SDValue();
// TODO: We should handle other cases of selecting between {-1,0,1} here.
if (CondVT == MVT::i1) {
// Only do this before legalization to avoid conflicting with target-specific
// transforms in the other direction (create a select from a zext/sext). There
// is also a target-independent combine here in DAGCombiner in the other
// direction for (select Cond, -1, 0) when the condition is not i1.
// TODO: This could be generalized for any 2 constants that differ by 1:
// add ({s/z}ext Cond), C
if (CondVT == MVT::i1 && !LegalOperations) {
if (isNullConstant(N1) && isOneConstant(N2)) {
// select Cond, 0, 1 --> zext (!Cond)
SDValue NotCond = DAG.getNOT(DL, Cond, MVT::i1);
@ -5608,6 +5613,25 @@ SDValue DAGCombiner::foldSelectOfConstants(SDNode *N) {
NotCond = DAG.getNode(ISD::ZERO_EXTEND, DL, VT, NotCond);
return NotCond;
}
if (isNullConstant(N1) && isAllOnesConstant(N2)) {
// select Cond, 0, -1 --> sext (!Cond)
SDValue NotCond = DAG.getNOT(DL, Cond, MVT::i1);
if (VT != MVT::i1)
NotCond = DAG.getNode(ISD::SIGN_EXTEND, DL, VT, NotCond);
return NotCond;
}
if (isOneConstant(N1) && isNullConstant(N2)) {
// select Cond, 1, 0 --> zext (Cond)
if (VT != MVT::i1)
Cond = DAG.getNode(ISD::ZERO_EXTEND, DL, VT, Cond);
return Cond;
}
if (isAllOnesConstant(N1) && isNullConstant(N2)) {
// select Cond, -1, 0 --> sext (Cond)
if (VT != MVT::i1)
Cond = DAG.getNode(ISD::SIGN_EXTEND, DL, VT, Cond);
return Cond;
}
return SDValue();
}
@ -6766,7 +6790,12 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
if (!VT.isVector()) {
EVT SetCCVT = getSetCCResultType(N00VT);
if (!LegalOperations || TLI.isOperationLegal(ISD::SETCC, N00VT)) {
// Don't do this transform for i1 because there's a select transform
// that would reverse it.
// TODO: We should not do this transform at all without a target hook
// because a sext is likely cheaper than a select?
if (SetCCVT.getScalarSizeInBits() != 1 &&
(!LegalOperations || TLI.isOperationLegal(ISD::SETCC, N00VT))) {
SDValue SetCC = DAG.getSetCC(DL, SetCCVT, N00, N01, CC);
return DAG.getSelect(DL, VT, SetCC, ExtTrueVal, Zero);
}

12
llvm/test/CodeGen/AMDGPU/trunc.ll
View File

@ -56,8 +56,7 @@ define void @trunc_shl_i64(i64 addrspace(1)* %out2, i32 addrspace(1)* %out, i64
}
; GCN-LABEL: {{^}}trunc_i32_to_i1:
; GCN: v_and_b32_e32 v{{[0-9]+}}, 1, v{{[0-9]+}}
; GCN: v_cmp_eq_u32
; GCN: v_and_b32_e32 [[VREG:v[0-9]+]], 1, v{{[0-9]+}}
define void @trunc_i32_to_i1(i32 addrspace(1)* %out, i32 addrspace(1)* %ptr) {
%a = load i32, i32 addrspace(1)* %ptr, align 4
%trunc = trunc i32 %a to i1
@ -67,8 +66,7 @@ define void @trunc_i32_to_i1(i32 addrspace(1)* %out, i32 addrspace(1)* %ptr) {
}
; GCN-LABEL: {{^}}trunc_i8_to_i1:
; GCN: v_and_b32_e32 v{{[0-9]+}}, 1, v{{[0-9]+}}
; GCN: v_cmp_eq_u32
; GCN: v_and_b32_e32 [[VREG:v[0-9]+]], 1, v{{[0-9]+}}
define void @trunc_i8_to_i1(i8 addrspace(1)* %out, i8 addrspace(1)* %ptr) {
%a = load i8, i8 addrspace(1)* %ptr, align 4
%trunc = trunc i8 %a to i1
@ -78,8 +76,7 @@ define void @trunc_i8_to_i1(i8 addrspace(1)* %out, i8 addrspace(1)* %ptr) {
}
; GCN-LABEL: {{^}}sgpr_trunc_i16_to_i1:
; GCN: s_and_b32 s{{[0-9]+}}, 1, s{{[0-9]+}}
; GCN: v_cmp_eq_u32
; GCN: s_and_b32 s{{[0-9]+}}, s{{[0-9]+}}, 1
define void @sgpr_trunc_i16_to_i1(i16 addrspace(1)* %out, i16 %a) {
%trunc = trunc i16 %a to i1
%result = select i1 %trunc, i16 1, i16 0
@ -88,8 +85,7 @@ define void @sgpr_trunc_i16_to_i1(i16 addrspace(1)* %out, i16 %a) {
}
; GCN-LABEL: {{^}}sgpr_trunc_i32_to_i1:
; GCN: s_and_b32 s{{[0-9]+}}, 1, s{{[0-9]+}}
; GCN: v_cmp_eq_u32
; GCN: s_and_b32 s{{[0-9]+}}, s{{[0-9]+}}, 1
define void @sgpr_trunc_i32_to_i1(i32 addrspace(1)* %out, i32 %a) {
%trunc = trunc i32 %a to i1
%result = select i1 %trunc, i32 1, i32 0

35
llvm/test/CodeGen/ARM/select_const.ll
View File

@ -40,8 +40,7 @@ define i32 @select_0_or_1_signext(i1 signext %cond) {
define i32 @select_1_or_0(i1 %cond) {
; CHECK-LABEL: select_1_or_0:
; CHECK: @ BB#0:
; CHECK-NEXT: ands r0, r0, #1
; CHECK-NEXT: movne r0, #1
; CHECK-NEXT: and r0, r0, #1
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 1, i32 0
ret i32 %sel
@ -50,8 +49,6 @@ define i32 @select_1_or_0(i1 %cond) {
define i32 @select_1_or_0_zeroext(i1 zeroext %cond) {
; CHECK-LABEL: select_1_or_0_zeroext:
; CHECK: @ BB#0:
; CHECK-NEXT: cmp r0, #0
; CHECK-NEXT: movne r0, #1
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 1, i32 0
ret i32 %sel
@ -60,8 +57,7 @@ define i32 @select_1_or_0_zeroext(i1 zeroext %cond) {
define i32 @select_1_or_0_signext(i1 signext %cond) {
; CHECK-LABEL: select_1_or_0_signext:
; CHECK: @ BB#0:
; CHECK-NEXT: ands r0, r0, #1
; CHECK-NEXT: movne r0, #1
; CHECK-NEXT: and r0, r0, #1
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 1, i32 0
ret i32 %sel
@ -72,10 +68,9 @@ define i32 @select_1_or_0_signext(i1 signext %cond) {
define i32 @select_0_or_neg1(i1 %cond) {
; CHECK-LABEL: select_0_or_neg1:
; CHECK: @ BB#0:
; CHECK-NEXT: mvn r1, #0
; CHECK-NEXT: tst r0, #1
; CHECK-NEXT: movne r1, #0
; CHECK-NEXT: mov r0, r1
; CHECK-NEXT: mov r1, #1
; CHECK-NEXT: bic r0, r1, r0
; CHECK-NEXT: rsb r0, r0, #0
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 0, i32 -1
ret i32 %sel
@ -84,10 +79,8 @@ define i32 @select_0_or_neg1(i1 %cond) {
define i32 @select_0_or_neg1_zeroext(i1 zeroext %cond) {
; CHECK-LABEL: select_0_or_neg1_zeroext:
; CHECK: @ BB#0:
; CHECK-NEXT: mvn r1, #0
; CHECK-NEXT: cmp r0, #0
; CHECK-NEXT: movne r1, #0
; CHECK-NEXT: mov r0, r1
; CHECK-NEXT: eor r0, r0, #1
; CHECK-NEXT: rsb r0, r0, #0
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 0, i32 -1
ret i32 %sel
@ -96,10 +89,7 @@ define i32 @select_0_or_neg1_zeroext(i1 zeroext %cond) {
define i32 @select_0_or_neg1_signext(i1 signext %cond) {
; CHECK-LABEL: select_0_or_neg1_signext:
; CHECK: @ BB#0:
; CHECK-NEXT: mvn r1, #0
; CHECK-NEXT: tst r0, #1
; CHECK-NEXT: movne r1, #0
; CHECK-NEXT: mov r0, r1
; CHECK-NEXT: mvn r0, r0
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 0, i32 -1
ret i32 %sel
@ -110,8 +100,8 @@ define i32 @select_0_or_neg1_signext(i1 signext %cond) {
define i32 @select_neg1_or_0(i1 %cond) {
; CHECK-LABEL: select_neg1_or_0:
; CHECK: @ BB#0:
; CHECK-NEXT: ands r0, r0, #1
; CHECK-NEXT: mvnne r0, #0
; CHECK-NEXT: and r0, r0, #1
; CHECK-NEXT: rsb r0, r0, #0
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 -1, i32 0
ret i32 %sel
@ -120,8 +110,7 @@ define i32 @select_neg1_or_0(i1 %cond) {
define i32 @select_neg1_or_0_zeroext(i1 zeroext %cond) {
; CHECK-LABEL: select_neg1_or_0_zeroext:
; CHECK: @ BB#0:
; CHECK-NEXT: cmp r0, #0
; CHECK-NEXT: mvnne r0, #0
; CHECK-NEXT: rsb r0, r0, #0
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 -1, i32 0
ret i32 %sel
@ -130,8 +119,6 @@ define i32 @select_neg1_or_0_zeroext(i1 zeroext %cond) {
define i32 @select_neg1_or_0_signext(i1 signext %cond) {
; CHECK-LABEL: select_neg1_or_0_signext:
; CHECK: @ BB#0:
; CHECK-NEXT: ands r0, r0, #1
; CHECK-NEXT: mvnne r0, #0
; CHECK-NEXT: mov pc, lr
%sel = select i1 %cond, i32 -1, i32 0
ret i32 %sel

9
llvm/test/CodeGen/Hexagon/adde.ll
View File

@ -1,13 +1,12 @@
; RUN: llc -march=hexagon -disable-hsdr -hexagon-expand-condsets=0 -hexagon-bit=0 -disable-post-ra < %s | FileCheck %s
; CHECK: r{{[0-9]+:[0-9]+}} = combine(#0,#1)
; CHECK: r{{[0-9]+:[0-9]+}} = combine(#0,#0)
; CHECK: r{{[0-9]+:[0-9]+}} = add(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = combine(#0,#1)
; CHECK: p{{[0-9]+}} = cmp.gtu(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: p{{[0-9]+}} = cmp.gtu(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},r{{[0-9]+}},r{{[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},r{{[0-9]+}},r{{[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = combine(r{{[0-9]+}},r{{[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},#1,#0)
; CHECK: r{{[0-9]+:[0-9]+}} = combine(#0,r{{[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = add(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},r{{[0-9]+}},r{{[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},r{{[0-9]+}},r{{[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = combine(r{{[0-9]+}},r{{[0-9]+}})

8
llvm/test/CodeGen/Hexagon/sube.ll
View File

@ -1,13 +1,11 @@
; RUN: llc -march=hexagon -disable-hsdr -hexagon-expand-condsets=0 -hexagon-bit=0 -disable-post-ra < %s | FileCheck %s
; CHECK: r{{[0-9]+:[0-9]+}} = combine(#0,#0)
; CHECK: r{{[0-9]+:[0-9]+}} = combine(#0,#1)
; CHECK: p{{[0-9]+}} = cmp.gtu(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = sub(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},r{{[0-9]+}},r{{[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},r{{[0-9]+}},r{{[0-9]+}})
; CHECK: r{{[0-9]+}} = mux(p{{[0-9]+}},#1,#0
; CHECK: r{{[0-9]+:[0-9]+}} = sub(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = combine(#0,r{{[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = sub(r{{[0-9]+:[0-9]+}},r{{[0-9]+:[0-9]+}})
; CHECK: r{{[0-9]+:[0-9]+}} = combine(r{{[0-9]+}},r{{[0-9]+}})
define void @check_sube_subc(i64 %AL, i64 %AH, i64 %BL, i64 %BH, i64* %RL, i64* %RH) {
entry:

2
llvm/test/CodeGen/NVPTX/add-128bit.ll
View File

@ -8,7 +8,7 @@ define void @foo(i64 %a, i64 %add, i128* %retptr) {
; CHECK: add.s64
; CHECK: setp.lt.u64
; CHECK: setp.lt.u64
; CHECK: selp.b64
; CHECK: selp.u64
; CHECK: selp.b64
; CHECK: add.s64
%t1 = sext i64 %a to i128

65
llvm/test/CodeGen/PowerPC/select_const.ll
View File

@ -39,70 +39,27 @@ define i32 @select_0_or_1_signext(i1 signext %cond) {
; select Cond, 1, 0 --> zext (Cond)
define i32 @select_1_or_0(i1 %cond) {
; ISEL-LABEL: select_1_or_0:
; ISEL: # BB#0:
; ISEL-NEXT: andi. 3, 3, 1
; ISEL-NEXT: li 4, 1
; ISEL-NEXT: li 3, 0
; ISEL-NEXT: isel 3, 4, 3, 1
; ISEL-NEXT: blr
;
; NO_ISEL-LABEL: select_1_or_0:
; NO_ISEL: # BB#0:
; NO_ISEL-NEXT: andi. 3, 3, 1
; NO_ISEL-NEXT: li 4, 1
; NO_ISEL-NEXT: li 3, 0
; NO_ISEL-NEXT: bc 12, 1, .LBB3_1
; NO_ISEL-NEXT: blr
; NO_ISEL-NEXT: .LBB3_1:
; NO_ISEL-NEXT: addi 3, 4, 0
; NO_ISEL-NEXT: blr
; ALL-LABEL: select_1_or_0:
; ALL: # BB#0:
; ALL-NEXT: clrldi 3, 3, 63
; ALL-NEXT: blr
%sel = select i1 %cond, i32 1, i32 0
ret i32 %sel
}
define i32 @select_1_or_0_zeroext(i1 zeroext %cond) {
; ISEL-LABEL: select_1_or_0_zeroext:
; ISEL: # BB#0:
; ISEL-NEXT: andi. 3, 3, 1
; ISEL-NEXT: li 4, 1
; ISEL-NEXT: li 3, 0
; ISEL-NEXT: isel 3, 4, 3, 1
; ISEL-NEXT: blr
;
; NO_ISEL-LABEL: select_1_or_0_zeroext:
; NO_ISEL: # BB#0:
; NO_ISEL-NEXT: andi. 3, 3, 1
; NO_ISEL-NEXT: li 4, 1
; NO_ISEL-NEXT: li 3, 0
; NO_ISEL-NEXT: bc 12, 1, .LBB4_1
; NO_ISEL-NEXT: blr
; NO_ISEL-NEXT: .LBB4_1:
; NO_ISEL-NEXT: addi 3, 4, 0
; NO_ISEL-NEXT: blr
; ALL-LABEL: select_1_or_0_zeroext:
; ALL: # BB#0:
; ALL-NEXT: blr
%sel = select i1 %cond, i32 1, i32 0
ret i32 %sel
}
define i32 @select_1_or_0_signext(i1 signext %cond) {
; ISEL-LABEL: select_1_or_0_signext:
; ISEL: # BB#0:
; ISEL-NEXT: andi. 3, 3, 1
; ISEL-NEXT: li 4, 1
; ISEL-NEXT: li 3, 0
; ISEL-NEXT: isel 3, 4, 3, 1
; ISEL-NEXT: blr
;
; NO_ISEL-LABEL: select_1_or_0_signext:
; NO_ISEL: # BB#0:
; NO_ISEL-NEXT: andi. 3, 3, 1
; NO_ISEL-NEXT: li 4, 1
; NO_ISEL-NEXT: li 3, 0
; NO_ISEL-NEXT: bc 12, 1, .LBB5_1
; NO_ISEL-NEXT: blr
; NO_ISEL-NEXT: .LBB5_1:
; NO_ISEL-NEXT: addi 3, 4, 0
; NO_ISEL-NEXT: blr
; ALL-LABEL: select_1_or_0_signext:
; ALL: # BB#0:
; ALL-NEXT: clrldi 3, 3, 63
; ALL-NEXT: blr
%sel = select i1 %cond, i32 1, i32 0
ret i32 %sel
}

18
llvm/test/CodeGen/X86/select_const.ll
View File

@ -108,10 +108,9 @@ define i32 @select_0_or_neg1_signext(i1 signext %cond) {
define i32 @select_neg1_or_0(i1 %cond) {
; CHECK-LABEL: select_neg1_or_0:
; CHECK: # BB#0:
; CHECK-NEXT: xorl %ecx, %ecx
; CHECK-NEXT: testb $1, %dil
; CHECK-NEXT: movl $-1, %eax
; CHECK-NEXT: cmovel %ecx, %eax
; CHECK-NEXT: andl $1, %edi
; CHECK-NEXT: negl %edi
; CHECK-NEXT: movl %edi, %eax
; CHECK-NEXT: retq
%sel = select i1 %cond, i32 -1, i32 0
ret i32 %sel
@ -120,10 +119,8 @@ define i32 @select_neg1_or_0(i1 %cond) {
define i32 @select_neg1_or_0_zeroext(i1 zeroext %cond) {
; CHECK-LABEL: select_neg1_or_0_zeroext:
; CHECK: # BB#0:
; CHECK-NEXT: xorl %ecx, %ecx
; CHECK-NEXT: testb %dil, %dil
; CHECK-NEXT: movl $-1, %eax
; CHECK-NEXT: cmovel %ecx, %eax
; CHECK-NEXT: movzbl %dil, %eax
; CHECK-NEXT: negl %eax
; CHECK-NEXT: retq
%sel = select i1 %cond, i32 -1, i32 0
ret i32 %sel
@ -132,10 +129,7 @@ define i32 @select_neg1_or_0_zeroext(i1 zeroext %cond) {
define i32 @select_neg1_or_0_signext(i1 signext %cond) {
; CHECK-LABEL: select_neg1_or_0_signext:
; CHECK: # BB#0:
; CHECK-NEXT: xorl %ecx, %ecx
; CHECK-NEXT: testb $1, %dil
; CHECK-NEXT: movl $-1, %eax
; CHECK-NEXT: cmovel %ecx, %eax
; CHECK-NEXT: movsbl %dil, %eax
; CHECK-NEXT: retq
%sel = select i1 %cond, i32 -1, i32 0
ret i32 %sel