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[InstCombine] hoist min/max intrinsics above select with constant op
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This is an extension of the handling for unary intrinsics and
follows the logic that we use for binary ops.

We don't canonicalize to min/max intrinsics yet, but this might
help unlock other folds seen in D98152.
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@rotateright
rotateright committed Jun 27, 2021
1 parent 81fcdae commit 153da08
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Showing 3 changed files with 27 additions and 23 deletions.
5 changes: 5 additions & 0 deletions llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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Expand Up @@ -1041,6 +1041,11 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
if (Instruction *Sel = foldClampRangeOfTwo(II, Builder))
return Sel;

if (match(I1, m_ImmConstant()))
if (auto *Sel = dyn_cast<SelectInst>(I0))
if (Instruction *R = FoldOpIntoSelect(*II, Sel))
return R;

break;
}
case Intrinsic::bswap: {
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17 changes: 10 additions & 7 deletions llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
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Expand Up @@ -942,13 +942,16 @@ static Value *foldOperationIntoSelectOperand(Instruction &I, Value *SO,
assert(canConstantFoldCallTo(II, cast<Function>(II->getCalledOperand())) &&
"Expected constant-foldable intrinsic");
Intrinsic::ID IID = II->getIntrinsicID();
SmallVector<Value *, 2> Args = {SO};

// Propagate the zero-is-undef argument to the new instruction.
if (IID == Intrinsic::ctlz || IID == Intrinsic::cttz)
Args.push_back(II->getArgOperand(1));

return Builder.CreateIntrinsic(IID, I.getType(), Args);
if (II->getNumArgOperands() == 1)
return Builder.CreateUnaryIntrinsic(IID, SO);

// This works for real binary ops like min/max (where we always expect the
// constant operand to be canonicalized as op1) and unary ops with a bonus
// constant argument like ctlz/cttz.
// TODO: Handle non-commutative binary intrinsics as below for binops.
assert(II->getNumArgOperands() == 2 && "Expected binary intrinsic");
assert(isa<Constant>(II->getArgOperand(1)) && "Expected constant operand");
return Builder.CreateBinaryIntrinsic(IID, SO, II->getArgOperand(1));
}

assert(I.isBinaryOp() && "Unexpected opcode for select folding");
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28 changes: 12 additions & 16 deletions llvm/test/Transforms/InstCombine/select-min-max.ll
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Expand Up @@ -111,8 +111,7 @@ define i5 @umin_umin_common_op_10_uses(i1 %cond, i5 %x, i5 %y, i5 %z, i5* %p1, i

define i5 @smin_select_const_const(i1 %b) {
; CHECK-LABEL: @smin_select_const_const(
; CHECK-NEXT: [[S:%.*]] = select i1 [[B:%.*]], i5 -3, i5 8
; CHECK-NEXT: [[C:%.*]] = call i5 @llvm.smin.i5(i5 [[S]], i5 5)
; CHECK-NEXT: [[C:%.*]] = select i1 [[B:%.*]], i5 -3, i5 5
; CHECK-NEXT: ret i5 [[C]]
;
%s = select i1 %b, i5 -3, i5 8
Expand All @@ -122,8 +121,7 @@ define i5 @smin_select_const_const(i1 %b) {

define <2 x i8> @smax_select_const_const(<2 x i1> %b) {
; CHECK-LABEL: @smax_select_const_const(
; CHECK-NEXT: [[S:%.*]] = select <2 x i1> [[B:%.*]], <2 x i8> <i8 1, i8 3>, <2 x i8> <i8 5, i8 43>
; CHECK-NEXT: [[C:%.*]] = call <2 x i8> @llvm.smax.v2i8(<2 x i8> [[S]], <2 x i8> <i8 0, i8 42>)
; CHECK-NEXT: [[C:%.*]] = select <2 x i1> [[B:%.*]], <2 x i8> <i8 1, i8 42>, <2 x i8> <i8 5, i8 43>
; CHECK-NEXT: ret <2 x i8> [[C]]
;
%s = select <2 x i1> %b, <2 x i8> <i8 1, i8 3>, <2 x i8> <i8 5, i8 43>
Expand All @@ -133,8 +131,7 @@ define <2 x i8> @smax_select_const_const(<2 x i1> %b) {

define i5 @umin_select_const_const(i1 %b) {
; CHECK-LABEL: @umin_select_const_const(
; CHECK-NEXT: [[S:%.*]] = select i1 [[B:%.*]], i5 8, i5 3
; CHECK-NEXT: [[C:%.*]] = call i5 @llvm.umin.i5(i5 [[S]], i5 4)
; CHECK-NEXT: [[C:%.*]] = select i1 [[B:%.*]], i5 4, i5 3
; CHECK-NEXT: ret i5 [[C]]
;
%s = select i1 %b, i5 8, i5 3
Expand All @@ -144,8 +141,7 @@ define i5 @umin_select_const_const(i1 %b) {

define <3 x i5> @umax_select_const_const(<3 x i1> %b) {
; CHECK-LABEL: @umax_select_const_const(
; CHECK-NEXT: [[S:%.*]] = select <3 x i1> [[B:%.*]], <3 x i5> <i5 2, i5 3, i5 4>, <3 x i5> <i5 7, i5 8, i5 9>
; CHECK-NEXT: [[C:%.*]] = call <3 x i5> @llvm.umax.v3i5(<3 x i5> [[S]], <3 x i5> <i5 5, i5 8, i5 -16>)
; CHECK-NEXT: [[C:%.*]] = select <3 x i1> [[B:%.*]], <3 x i5> <i5 5, i5 8, i5 -16>, <3 x i5> <i5 7, i5 8, i5 -16>
; CHECK-NEXT: ret <3 x i5> [[C]]
;
%s = select <3 x i1> %b, <3 x i5> <i5 2, i5 3, i5 4>, <3 x i5> <i5 7, i5 8, i5 9>
Expand All @@ -155,8 +151,8 @@ define <3 x i5> @umax_select_const_const(<3 x i1> %b) {

define i5 @smin_select_const(i1 %b, i5 %x) {
; CHECK-LABEL: @smin_select_const(
; CHECK-NEXT: [[S:%.*]] = select i1 [[B:%.*]], i5 -3, i5 [[X:%.*]]
; CHECK-NEXT: [[C:%.*]] = call i5 @llvm.smin.i5(i5 [[S]], i5 5)
; CHECK-NEXT: [[TMP1:%.*]] = call i5 @llvm.smin.i5(i5 [[X:%.*]], i5 5)
; CHECK-NEXT: [[C:%.*]] = select i1 [[B:%.*]], i5 -3, i5 [[TMP1]]
; CHECK-NEXT: ret i5 [[C]]
;
%s = select i1 %b, i5 -3, i5 %x
Expand All @@ -166,8 +162,8 @@ define i5 @smin_select_const(i1 %b, i5 %x) {

define <2 x i8> @smax_select_const(<2 x i1> %b, <2 x i8> %x) {
; CHECK-LABEL: @smax_select_const(
; CHECK-NEXT: [[S:%.*]] = select <2 x i1> [[B:%.*]], <2 x i8> [[X:%.*]], <2 x i8> <i8 5, i8 43>
; CHECK-NEXT: [[C:%.*]] = call <2 x i8> @llvm.smax.v2i8(<2 x i8> [[S]], <2 x i8> <i8 0, i8 42>)
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i8> @llvm.smax.v2i8(<2 x i8> [[X:%.*]], <2 x i8> <i8 0, i8 42>)
; CHECK-NEXT: [[C:%.*]] = select <2 x i1> [[B:%.*]], <2 x i8> [[TMP1]], <2 x i8> <i8 5, i8 43>
; CHECK-NEXT: ret <2 x i8> [[C]]
;
%s = select <2 x i1> %b, <2 x i8> %x, <2 x i8> <i8 5, i8 43>
Expand All @@ -177,8 +173,8 @@ define <2 x i8> @smax_select_const(<2 x i1> %b, <2 x i8> %x) {

define i5 @umin_select_const(i1 %b, i5 %x) {
; CHECK-LABEL: @umin_select_const(
; CHECK-NEXT: [[S:%.*]] = select i1 [[B:%.*]], i5 [[X:%.*]], i5 3
; CHECK-NEXT: [[C:%.*]] = call i5 @llvm.umin.i5(i5 [[S]], i5 4)
; CHECK-NEXT: [[TMP1:%.*]] = call i5 @llvm.umin.i5(i5 [[X:%.*]], i5 4)
; CHECK-NEXT: [[C:%.*]] = select i1 [[B:%.*]], i5 [[TMP1]], i5 3
; CHECK-NEXT: ret i5 [[C]]
;
%s = select i1 %b, i5 %x, i5 3
Expand All @@ -188,8 +184,8 @@ define i5 @umin_select_const(i1 %b, i5 %x) {

define <3 x i5> @umax_select_const(<3 x i1> %b, <3 x i5> %x) {
; CHECK-LABEL: @umax_select_const(
; CHECK-NEXT: [[S:%.*]] = select <3 x i1> [[B:%.*]], <3 x i5> <i5 2, i5 3, i5 4>, <3 x i5> [[X:%.*]]
; CHECK-NEXT: [[C:%.*]] = call <3 x i5> @llvm.umax.v3i5(<3 x i5> [[S]], <3 x i5> <i5 5, i5 8, i5 1>)
; CHECK-NEXT: [[TMP1:%.*]] = call <3 x i5> @llvm.umax.v3i5(<3 x i5> [[X:%.*]], <3 x i5> <i5 5, i5 8, i5 1>)
; CHECK-NEXT: [[C:%.*]] = select <3 x i1> [[B:%.*]], <3 x i5> <i5 5, i5 8, i5 4>, <3 x i5> [[TMP1]]
; CHECK-NEXT: ret <3 x i5> [[C]]
;
%s = select <3 x i1> %b, <3 x i5> <i5 2, i5 3, i5 4>, <3 x i5> %x
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