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Optimize icmp involving addition better

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Allows LLVM to optimize sequences like the following:

%add = add nsw i32 %x, 1
%cmp = icmp sgt i32 %add, %y

into:

%cmp = icmp sge i32 %x, %y

as well as:

%add1 = add nsw i32 %x, 20
%add2 = add nsw i32 %y, 57
%cmp = icmp sge i32 %add1, %add2

into:

%add = add nsw i32 %y, 37
%cmp = icmp sle i32 %cmp, %x


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179316 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2013-04-11 20:05:46 +00:00
parent efc8740647
commit 59b11c415e
2 changed files with 101 additions and 0 deletions
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49
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2487,6 +2487,55 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return new ICmpInst(Pred, Y, Z);
}
// icmp slt (X + -1), Y -> icmp sle X, Y
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
match(B, m_AllOnes()))
return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
// icmp sge (X + -1), Y -> icmp sgt X, Y
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
match(B, m_AllOnes()))
return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
// icmp sle (X + 1), Y -> icmp slt X, Y
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE &&
match(B, m_One()))
return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
// icmp sgt (X + 1), Y -> icmp sge X, Y
if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT &&
match(B, m_One()))
return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
// if C1 has greater magnitude than C2:
// icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
// s.t. C3 = C1 - C2
//
// if C2 has greater magnitude than C1:
// icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
// s.t. C3 = C2 - C1
if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
(BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
const APInt &AP1 = C1->getValue();
const APInt &AP2 = C2->getValue();
if (AP1.isNegative() == AP2.isNegative()) {
APInt AP1Abs = C1->getValue().abs();
APInt AP2Abs = C2->getValue().abs();
if (AP1Abs.uge(AP2Abs)) {
ConstantInt *C3 = Builder->getInt(AP1 - AP2);
Value *NewAdd = Builder->CreateNSWAdd(A, C3);
return new ICmpInst(Pred, NewAdd, C);
} else {
ConstantInt *C3 = Builder->getInt(AP2 - AP1);
Value *NewAdd = Builder->CreateNSWAdd(C, C3);
return new ICmpInst(Pred, A, NewAdd);
}
}
}
// Analyze the case when either Op0 or Op1 is a sub instruction.
// Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
A = 0; B = 0; C = 0; D = 0;

52
test/Transforms/InstCombine/icmp.ll
View File

@ -886,3 +886,55 @@ define i1 @icmp_mul0_ne0(i32 %x) {
%cmp = icmp ne i32 %mul, 0
ret i1 %cmp
}
; CHECK: @icmp_sub1_sge
; CHECK-NEXT: icmp sgt i32 %x, %y
define i1 @icmp_sub1_sge(i32 %x, i32 %y) {
%sub = add nsw i32 %x, -1
%cmp = icmp sge i32 %sub, %y
ret i1 %cmp
}
; CHECK: @icmp_add1_sgt
; CHECK-NEXT: icmp sge i32 %x, %y
define i1 @icmp_add1_sgt(i32 %x, i32 %y) {
%add = add nsw i32 %x, 1
%cmp = icmp sgt i32 %add, %y
ret i1 %cmp
}
; CHECK: @icmp_sub1_slt
; CHECK-NEXT: icmp sle i32 %x, %y
define i1 @icmp_sub1_slt(i32 %x, i32 %y) {
%sub = add nsw i32 %x, -1
%cmp = icmp slt i32 %sub, %y
ret i1 %cmp
}
; CHECK: @icmp_add1_sle
; CHECK-NEXT: icmp slt i32 %x, %y
define i1 @icmp_add1_sle(i32 %x, i32 %y) {
%add = add nsw i32 %x, 1
%cmp = icmp sle i32 %add, %y
ret i1 %cmp
}
; CHECK: @icmp_add20_sge_add57
; CHECK-NEXT: [[ADD:%[a-z0-9]+]] = add nsw i32 %y, 37
; CHECK-NEXT: icmp sle i32 [[ADD]], %x
define i1 @icmp_add20_sge_add57(i32 %x, i32 %y) {
%1 = add nsw i32 %x, 20
%2 = add nsw i32 %y, 57
%cmp = icmp sge i32 %1, %2
ret i1 %cmp
}
; CHECK: @icmp_sub57_sge_sub20
; CHECK-NEXT: [[SUB:%[a-z0-9]+]] = add nsw i32 %x, -37
; CHECK-NEXT: icmp sge i32 [[SUB]], %y
define i1 @icmp_sub57_sge_sub20(i32 %x, i32 %y) {
%1 = add nsw i32 %x, -57
%2 = add nsw i32 %y, -20
%cmp = icmp sge i32 %1, %2
ret i1 %cmp
}