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[InstCombine] Fold icmp eq/ne (udiv i32 A, B), 0 -> icmp ugt/ule B, A.

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Differential Revision: http://reviews.llvm.org/D20036

llvm-svn: 268960
This commit is contained in:
Chad Rosier 2016-05-09 19:30:20 +00:00
parent 89c9635b0a
commit 8b41062bd4
3 changed files with 61 additions and 0 deletions
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12
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -2105,6 +2105,8 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI),
DivRHS))
return R;
// FIXME: Handle (icmp ugt (udiv i32 CI2, A), CI) and
// (icmp ult (udiv i32 CI2, A), CI).
break;
case Instruction::Sub: {
@ -3583,12 +3585,22 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// See if we are doing a comparison between a constant and an instruction that
// can be folded into the comparison.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
Value *A = nullptr, *B = nullptr;
// Since the RHS is a ConstantInt (CI), if the left hand side is an
// instruction, see if that instruction also has constants so that the
// instruction can be folded into the icmp
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI))
return Res;
// (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
if (I.isEquality() && CI->isZero() &&
match(Op0, m_UDiv(m_Value(A), m_Value(B)))) {
ICmpInst::Predicate Pred = I.getPredicate() == ICmpInst::ICMP_EQ
? ICmpInst::ICMP_UGT
: ICmpInst::ICMP_ULE;
return new ICmpInst(Pred, B, A);
}
}
// Handle icmp with constant (but not simple integer constant) RHS

41
test/Transforms/InstCombine/compare-udiv.ll Normal file
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@ -0,0 +1,41 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; CHECK-LABEL: @test1
; CHECK: %cmp1 = icmp ugt i32 %d, %n
define i1 @test1(i32 %n, i32 %d) {
%div = udiv i32 %n, %d
%cmp1 = icmp eq i32 %div, 0
ret i1 %cmp1
}
; CHECK-LABEL: @test2
; CHECK: %cmp1 = icmp ugt i32 %d, 64
define i1 @test2(i32 %d) {
%div = udiv i32 64, %d
%cmp1 = icmp eq i32 %div, 0
ret i1 %cmp1
}
; CHECK-LABEL: @test3
; CHECK: %cmp1 = icmp ule i32 %d, %n
define i1 @test3(i32 %n, i32 %d) {
%div = udiv i32 %n, %d
%cmp1 = icmp ne i32 %div, 0
ret i1 %cmp1
}
; CHECK-LABEL: @test4
; CHECK: %cmp1 = icmp ult i32 %d, 65
define i1 @test4(i32 %d) {
%div = udiv i32 64, %d
%cmp1 = icmp ne i32 %div, 0
ret i1 %cmp1
}
; CHECK-LABEL: @test5
; CHECK: ret i1 true
define i1 @test5(i32 %d) {
%div = udiv i32 -1, %d
%cmp1 = icmp ne i32 %div, 0
ret i1 %cmp1
}

8
test/Transforms/InstCombine/exact.ll
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@ -121,6 +121,14 @@ define i1 @udiv_icmp1(i64 %X) nounwind {
ret i1 %B
}
; CHECK-LABEL: @udiv_icmp2(
; CHECK: icmp eq i64 %X, 0
define i1 @udiv_icmp2(i64 %X) nounwind {
%A = udiv exact i64 %X, 5 ; X/5 == 0 --> x == 0
%B = icmp eq i64 %A, 0
ret i1 %B
}
; CHECK-LABEL: @sdiv_icmp1(
; CHECK: icmp eq i64 %X, 0
define i1 @sdiv_icmp1(i64 %X) nounwind {