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[InstSimplify] fold icmp with mul nuw and constant operands

Browse Source 
https://rise4fun.com/Alive/pZEr

  Name: mul nuw with icmp eq
  Pre: (C2 %u C1) != 0
  %a = mul nuw i8 %x, C1
  %r = icmp eq i8 %a, C2
    =>
  %r = false

  Name: mul nuw with icmp ne
  Pre: (C2 %u C1) != 0
  %a = mul nuw i8 %x, C1
  %r = icmp ne i8 %a, C2
    =>
  %r = true

There are potentially several other transforms we need to add based on:
D51625
...but it doesn't look like there was follow-up to that patch.
This commit is contained in:
Sanjay Patel 2020-08-05 13:41:05 -04:00
parent f3548b0c21
commit 60815c576a
3 changed files with 29 additions and 21 deletions
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8
lib/Analysis/InstructionSimplify.cpp
View File

@ -2750,6 +2750,14 @@ static Value *simplifyICmpWithConstant(CmpInst::Predicate Pred, Value *LHS,
return ConstantInt::getFalse(ITy);
}
// (mul nuw X, MulC) != C --> true (if C is not a multiple of MulC)
// (mul nuw X, MulC) == C --> false (if C is not a multiple of MulC)
const APInt *MulC;
if (ICmpInst::isEquality(Pred) &&
match(LHS, m_NUWMul(m_Value(), m_APIntAllowUndef(MulC))) &&
C->urem(*MulC) != 0)
return ConstantInt::get(ITy, Pred == ICmpInst::ICMP_NE);
return nullptr;
}

8
test/Transforms/InstCombine/icmp-mul.ll
View File

@ -141,9 +141,7 @@ define i1 @ne_rem_zero(i8 %x) {
define i1 @eq_rem_nz(i8 %x) {
; CHECK-LABEL: @eq_rem_nz(
; CHECK-NEXT: [[A:%.*]] = mul nuw i8 [[X:%.*]], 5
; CHECK-NEXT: [[B:%.*]] = icmp eq i8 [[A]], 31
; CHECK-NEXT: ret i1 [[B]]
; CHECK-NEXT: ret i1 false
;
%a = mul nuw i8 %x, 5
%b = icmp eq i8 %a, 31
@ -152,9 +150,7 @@ define i1 @eq_rem_nz(i8 %x) {
define i1 @ne_rem_nz(i8 %x) {
; CHECK-LABEL: @ne_rem_nz(
; CHECK-NEXT: [[A:%.*]] = mul nuw i8 [[X:%.*]], 5
; CHECK-NEXT: [[B:%.*]] = icmp ne i8 [[A]], 31
; CHECK-NEXT: ret i1 [[B]]
; CHECK-NEXT: ret i1 true
;
%a = mul nuw i8 %x, 5
%b = icmp ne i8 %a, 31

34
test/Transforms/InstSimplify/icmp-constant.ll
View File

@ -810,11 +810,11 @@ define i1 @eq_shl_by_variable_produces_poison(i8 %x) {
ret i1 %cmp
}
; No overflow, so mul constant must be a factor of cmp constant.
define i1 @mul_nuw_urem_cmp_constant1(i8 %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_constant1(
; CHECK-NEXT: [[M:%.*]] = mul nuw i8 [[X:%.*]], 43
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[M]], 42
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 false
;
%m = mul nuw i8 %x, 43
%r = icmp eq i8 %m, 42
@ -825,31 +825,29 @@ define i1 @mul_nuw_urem_cmp_constant1(i8 %x) {
define <2 x i1> @mul_nuw_urem_cmp_constant_vec_splat(<2 x i8> %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_constant_vec_splat(
; CHECK-NEXT: [[M:%.*]] = mul nuw <2 x i8> [[X:%.*]], <i8 45, i8 45>
; CHECK-NEXT: [[R:%.*]] = icmp ne <2 x i8> [[M]], <i8 15, i8 15>
; CHECK-NEXT: ret <2 x i1> [[R]]
; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
;
%m = mul nuw <2 x i8> %x, <i8 45, i8 45>
%r = icmp ne <2 x i8> %m, <i8 15, i8 15>
ret <2 x i1> %r
}
; Undefs in vector constants are ok.
define <2 x i1> @mul_nuw_urem_cmp_constant_vec_splat_undef1(<2 x i8> %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_constant_vec_splat_undef1(
; CHECK-NEXT: [[M:%.*]] = mul nuw <2 x i8> [[X:%.*]], <i8 45, i8 45>
; CHECK-NEXT: [[R:%.*]] = icmp ne <2 x i8> [[M]], <i8 15, i8 undef>
; CHECK-NEXT: ret <2 x i1> [[R]]
; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
;
%m = mul nuw <2 x i8> %x, <i8 45, i8 45>
%r = icmp ne <2 x i8> %m, <i8 15, i8 undef>
ret <2 x i1> %r
}
; Undefs in vector constants are ok.
define <2 x i1> @mul_nuw_urem_cmp_constant_vec_splat_undef2(<2 x i8> %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_constant_vec_splat_undef2(
; CHECK-NEXT: [[M:%.*]] = mul nuw <2 x i8> [[X:%.*]], <i8 undef, i8 45>
; CHECK-NEXT: [[R:%.*]] = icmp ne <2 x i8> [[M]], <i8 15, i8 15>
; CHECK-NEXT: ret <2 x i1> [[R]]
; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
;
%m = mul nuw <2 x i8> %x, <i8 undef, i8 45>
%r = icmp ne <2 x i8> %m, <i8 15, i8 15>
@ -860,15 +858,15 @@ define <2 x i1> @mul_nuw_urem_cmp_constant_vec_splat_undef2(<2 x i8> %x) {
define i1 @mul_nuw_urem_cmp_constant2(i8 %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_constant2(
; CHECK-NEXT: [[M:%.*]] = mul nuw i8 [[X:%.*]], -42
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[M]], -84
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 false
;
%m = mul nuw i8 %x, -42
%r = icmp eq i8 %m, -84
ret i1 %r
}
; Negative test - require nuw.
define i1 @mul_urem_cmp_constant1(i8 %x) {
; CHECK-LABEL: @mul_urem_cmp_constant1(
; CHECK-NEXT: [[M:%.*]] = mul i8 [[X:%.*]], 43
@ -880,6 +878,8 @@ define i1 @mul_urem_cmp_constant1(i8 %x) {
ret i1 %r
}
; Negative test - x could be 0.
define i1 @mul_nuw_urem_cmp_constant0(i8 %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_constant0(
; CHECK-NEXT: [[M:%.*]] = mul nuw i8 [[X:%.*]], 23
@ -891,6 +891,8 @@ define i1 @mul_nuw_urem_cmp_constant0(i8 %x) {
ret i1 %r
}
; Negative test - cmp constant is multiple of mul constant.
define i1 @mul_nuw_urem_cmp_constant_is_0(i8 %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_constant_is_0(
; CHECK-NEXT: [[M:%.*]] = mul nuw i8 [[X:%.*]], 42
@ -902,6 +904,8 @@ define i1 @mul_nuw_urem_cmp_constant_is_0(i8 %x) {
ret i1 %r
}
; Negative test - cmp constant is multiple (treated as unsigned).
define i1 @mul_nuw_urem_cmp_neg_constant_is_0(i8 %x) {
; CHECK-LABEL: @mul_nuw_urem_cmp_neg_constant_is_0(
; CHECK-NEXT: [[M:%.*]] = mul nuw i8 [[X:%.*]], 43