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[InstCombine] optimize unsigned icmp of increment
Allows LLVM to optimize sequences like the following: %add = add nuw i32 %x, 1 %cmp = icmp ugt i32 %add, %y Into: %cmp = icmp uge i32 %x, %y Previously, only signed comparisons were being handled. Decrements could also be handled, but 'sub nuw %x, 1' is currently canonicalized to 'add %x, -1' in InstCombineAddSub, losing the nuw flag. Removing that canonicalization seems like it might have far-reaching ramifications so I kept this simple for now. Patch by Matti Niemenmaa! Differential Revision: https://reviews.llvm.org/D24700 llvm-svn: 291975
This commit is contained in:
Sanjay Patel
parent
ead291ba07
commit
c20cf10406
@ -2843,6 +2843,31 @@ Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
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if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
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return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
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// TODO: The subtraction-related identities shown below also hold, but
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// canonicalization from (X -nuw 1) to (X + -1) means that the combinations
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// wouldn't happen even if they were implemented.
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//
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// icmp ult (X - 1), Y -> icmp ule X, Y
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// icmp uge (X - 1), Y -> icmp ugt X, Y
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// icmp ugt X, (Y - 1) -> icmp uge X, Y
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// icmp ule X, (Y - 1) -> icmp ult X, Y
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// icmp ule (X + 1), Y -> icmp ult X, Y
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if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
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return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
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// icmp ugt (X + 1), Y -> icmp uge X, Y
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if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
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return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
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// icmp uge X, (Y + 1) -> icmp ugt X, Y
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if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
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return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
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// icmp ult X, (Y + 1) -> icmp ule X, Y
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if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
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return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
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// if C1 has greater magnitude than C2:
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// icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
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// s.t. C3 = C1 - C2
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@ -2425,6 +2425,10 @@ define i1 @f10(i16 %p) {
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ret i1 %cmp580
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}
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; Note: fptosi is used in various tests below to ensure that operand complexity
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; canonicalization does not kick in, which would make some of the tests
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; equivalent to one another.
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define i1 @cmp_sgt_rhs_dec(float %x, i32 %i) {
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; CHECK-LABEL: @cmp_sgt_rhs_dec(
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; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
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@ -2711,3 +2715,143 @@ define i1 @or_ptrtoint_mismatch(i8* %p, i32* %q) {
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%b = icmp eq i64 %o, 0
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ret i1 %b
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}
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define i1 @icmp_add1_ugt(i32 %x, i32 %y) {
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; CHECK-LABEL: @icmp_add1_ugt(
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; CHECK-NEXT: [[CMP:%.*]] = icmp uge i32 %x, %y
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%add = add nuw i32 %x, 1
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%cmp = icmp ugt i32 %add, %y
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ret i1 %cmp
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}
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define i1 @icmp_add1_ule(i32 %x, i32 %y) {
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; CHECK-LABEL: @icmp_add1_ule(
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; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 %x, %y
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%add = add nuw i32 %x, 1
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%cmp = icmp ule i32 %add, %y
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ret i1 %cmp
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}
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define i1 @cmp_uge_rhs_inc(float %x, i32 %i) {
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; CHECK-LABEL: @cmp_uge_rhs_inc(
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; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
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; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[CONV]], %i
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%conv = fptosi float %x to i32
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%inc = add nuw i32 %i, 1
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%cmp = icmp uge i32 %conv, %inc
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ret i1 %cmp
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}
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define i1 @cmp_ult_rhs_inc(float %x, i32 %i) {
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; CHECK-LABEL: @cmp_ult_rhs_inc(
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; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
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; CHECK-NEXT: [[CMP:%.*]] = icmp ule i32 [[CONV]], %i
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%conv = fptosi float %x to i32
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%inc = add nuw i32 %i, 1
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%cmp = icmp ult i32 %conv, %inc
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ret i1 %cmp
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}
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define i1 @cmp_sge_lhs_inc(i32 %x, i32 %y) {
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; CHECK-LABEL: @cmp_sge_lhs_inc(
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; CHECK-NEXT: [[INC:%.*]] = add
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; CHECK-NEXT: [[CMP:%.*]] = icmp sge i32 [[INC]], %y
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%inc = add nsw i32 %x, 1
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%cmp = icmp sge i32 %inc, %y
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ret i1 %cmp
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}
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define i1 @cmp_uge_lhs_inc(i32 %x, i32 %y) {
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; CHECK-LABEL: @cmp_uge_lhs_inc(
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; CHECK-NEXT: [[INC:%.*]] = add
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; CHECK-NEXT: [[CMP:%.*]] = icmp uge i32 [[INC]], %y
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%inc = add nuw i32 %x, 1
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%cmp = icmp uge i32 %inc, %y
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ret i1 %cmp
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}
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define i1 @cmp_sgt_lhs_dec(i32 %x, i32 %y) {
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; CHECK-LABEL: @cmp_sgt_lhs_dec(
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; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
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; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[DEC]], %y
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%dec = sub nsw i32 %x, 1
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%cmp = icmp sgt i32 %dec, %y
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ret i1 %cmp
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}
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define i1 @cmp_ugt_lhs_dec(i32 %x, i32 %y) {
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; CHECK-LABEL: @cmp_ugt_lhs_dec(
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; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
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; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[DEC]], %y
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%dec = sub nuw i32 %x, 1
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%cmp = icmp ugt i32 %dec, %y
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ret i1 %cmp
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}
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define i1 @cmp_sle_rhs_inc(float %x, i32 %y) {
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; CHECK-LABEL: @cmp_sle_rhs_inc(
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; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
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; CHECK-NEXT: [[INC:%.*]] = add
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; CHECK-NEXT: [[CMP:%.*]] = icmp sle i32 [[CONV]], [[INC]]
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%conv = fptosi float %x to i32
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%inc = add nsw i32 %y, 1
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%cmp = icmp sle i32 %conv, %inc
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ret i1 %cmp
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}
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define i1 @cmp_ule_rhs_inc(float %x, i32 %y) {
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; CHECK-LABEL: @cmp_ule_rhs_inc(
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; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
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; CHECK-NEXT: [[INC:%.*]] = add
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; CHECK-NEXT: [[CMP:%.*]] = icmp ule i32 [[CONV]], [[INC]]
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%conv = fptosi float %x to i32
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%inc = add nuw i32 %y, 1
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%cmp = icmp ule i32 %conv, %inc
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ret i1 %cmp
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}
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define i1 @cmp_slt_rhs_dec(float %x, i32 %y) {
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; CHECK-LABEL: @cmp_slt_rhs_dec(
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; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
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; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[CONV]], [[DEC]]
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%conv = fptosi float %x to i32
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%dec = sub nsw i32 %y, 1
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%cmp = icmp slt i32 %conv, %dec
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ret i1 %cmp
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}
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define i1 @cmp_ult_rhs_dec(float %x, i32 %y) {
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; CHECK-LABEL: @cmp_ult_rhs_dec(
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; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
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; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
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; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[CONV]], [[DEC]]
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%conv = fptosi float %x to i32
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%dec = sub nuw i32 %y, 1
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%cmp = icmp ult i32 %conv, %dec
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ret i1 %cmp
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}
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