[llvm] r291975 - [InstCombine] optimize unsigned icmp of increment
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 13 15:25:46 PST 2017
Author: spatel
Date: Fri Jan 13 17:25:46 2017
New Revision: 291975
URL: http://llvm.org/viewvc/llvm-project?rev=291975&view=rev
Log:
[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
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/test/Transforms/InstCombine/icmp.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=291975&r1=291974&r2=291975&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Fri Jan 13 17:25:46 2017
@@ -2843,6 +2843,31 @@ Instruction *InstCombiner::foldICmpBinOp
if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
+ // TODO: The subtraction-related identities shown below also hold, but
+ // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
+ // wouldn't happen even if they were implemented.
+ //
+ // icmp ult (X - 1), Y -> icmp ule X, Y
+ // icmp uge (X - 1), Y -> icmp ugt X, Y
+ // icmp ugt X, (Y - 1) -> icmp uge X, Y
+ // icmp ule X, (Y - 1) -> icmp ult X, Y
+
+ // icmp ule (X + 1), Y -> icmp ult X, Y
+ if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
+ return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
+
+ // icmp ugt (X + 1), Y -> icmp uge X, Y
+ if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
+ return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
+
+ // icmp uge X, (Y + 1) -> icmp ugt X, Y
+ if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
+ return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
+
+ // icmp ult X, (Y + 1) -> icmp ule X, Y
+ if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
+ return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
+
// if C1 has greater magnitude than C2:
// icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
// s.t. C3 = C1 - C2
Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=291975&r1=291974&r2=291975&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Fri Jan 13 17:25:46 2017
@@ -2425,6 +2425,10 @@ define i1 @f10(i16 %p) {
ret i1 %cmp580
}
+; Note: fptosi is used in various tests below to ensure that operand complexity
+; canonicalization does not kick in, which would make some of the tests
+; equivalent to one another.
+
define i1 @cmp_sgt_rhs_dec(float %x, i32 %i) {
; CHECK-LABEL: @cmp_sgt_rhs_dec(
; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
@@ -2711,3 +2715,143 @@ define i1 @or_ptrtoint_mismatch(i8* %p,
%b = icmp eq i64 %o, 0
ret i1 %b
}
+
+define i1 @icmp_add1_ugt(i32 %x, i32 %y) {
+; CHECK-LABEL: @icmp_add1_ugt(
+; CHECK-NEXT: [[CMP:%.*]] = icmp uge i32 %x, %y
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %add = add nuw i32 %x, 1
+ %cmp = icmp ugt i32 %add, %y
+ ret i1 %cmp
+}
+
+define i1 @icmp_add1_ule(i32 %x, i32 %y) {
+; CHECK-LABEL: @icmp_add1_ule(
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 %x, %y
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %add = add nuw i32 %x, 1
+ %cmp = icmp ule i32 %add, %y
+ ret i1 %cmp
+}
+
+define i1 @cmp_uge_rhs_inc(float %x, i32 %i) {
+; CHECK-LABEL: @cmp_uge_rhs_inc(
+; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[CONV]], %i
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %conv = fptosi float %x to i32
+ %inc = add nuw i32 %i, 1
+ %cmp = icmp uge i32 %conv, %inc
+ ret i1 %cmp
+}
+
+define i1 @cmp_ult_rhs_inc(float %x, i32 %i) {
+; CHECK-LABEL: @cmp_ult_rhs_inc(
+; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
+; CHECK-NEXT: [[CMP:%.*]] = icmp ule i32 [[CONV]], %i
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %conv = fptosi float %x to i32
+ %inc = add nuw i32 %i, 1
+ %cmp = icmp ult i32 %conv, %inc
+ ret i1 %cmp
+}
+
+define i1 @cmp_sge_lhs_inc(i32 %x, i32 %y) {
+; CHECK-LABEL: @cmp_sge_lhs_inc(
+; CHECK-NEXT: [[INC:%.*]] = add
+; CHECK-NEXT: [[CMP:%.*]] = icmp sge i32 [[INC]], %y
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %inc = add nsw i32 %x, 1
+ %cmp = icmp sge i32 %inc, %y
+ ret i1 %cmp
+}
+
+define i1 @cmp_uge_lhs_inc(i32 %x, i32 %y) {
+; CHECK-LABEL: @cmp_uge_lhs_inc(
+; CHECK-NEXT: [[INC:%.*]] = add
+; CHECK-NEXT: [[CMP:%.*]] = icmp uge i32 [[INC]], %y
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %inc = add nuw i32 %x, 1
+ %cmp = icmp uge i32 %inc, %y
+ ret i1 %cmp
+}
+
+define i1 @cmp_sgt_lhs_dec(i32 %x, i32 %y) {
+; CHECK-LABEL: @cmp_sgt_lhs_dec(
+; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[DEC]], %y
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %dec = sub nsw i32 %x, 1
+ %cmp = icmp sgt i32 %dec, %y
+ ret i1 %cmp
+}
+
+define i1 @cmp_ugt_lhs_dec(i32 %x, i32 %y) {
+; CHECK-LABEL: @cmp_ugt_lhs_dec(
+; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i32 [[DEC]], %y
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %dec = sub nuw i32 %x, 1
+ %cmp = icmp ugt i32 %dec, %y
+ ret i1 %cmp
+}
+
+define i1 @cmp_sle_rhs_inc(float %x, i32 %y) {
+; CHECK-LABEL: @cmp_sle_rhs_inc(
+; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
+; CHECK-NEXT: [[INC:%.*]] = add
+; CHECK-NEXT: [[CMP:%.*]] = icmp sle i32 [[CONV]], [[INC]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %conv = fptosi float %x to i32
+ %inc = add nsw i32 %y, 1
+ %cmp = icmp sle i32 %conv, %inc
+ ret i1 %cmp
+}
+
+define i1 @cmp_ule_rhs_inc(float %x, i32 %y) {
+; CHECK-LABEL: @cmp_ule_rhs_inc(
+; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
+; CHECK-NEXT: [[INC:%.*]] = add
+; CHECK-NEXT: [[CMP:%.*]] = icmp ule i32 [[CONV]], [[INC]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %conv = fptosi float %x to i32
+ %inc = add nuw i32 %y, 1
+ %cmp = icmp ule i32 %conv, %inc
+ ret i1 %cmp
+}
+
+define i1 @cmp_slt_rhs_dec(float %x, i32 %y) {
+; CHECK-LABEL: @cmp_slt_rhs_dec(
+; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
+; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[CONV]], [[DEC]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %conv = fptosi float %x to i32
+ %dec = sub nsw i32 %y, 1
+ %cmp = icmp slt i32 %conv, %dec
+ ret i1 %cmp
+}
+
+define i1 @cmp_ult_rhs_dec(float %x, i32 %y) {
+; CHECK-LABEL: @cmp_ult_rhs_dec(
+; CHECK-NEXT: [[CONV:%.*]] = fptosi float %x to i32
+; CHECK-NEXT: [[DEC:%.*]] = {{add|sub}}
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[CONV]], [[DEC]]
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %conv = fptosi float %x to i32
+ %dec = sub nuw i32 %y, 1
+ %cmp = icmp ult i32 %conv, %dec
+ ret i1 %cmp
+}
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