[llvm] f879c9b - [InstSimplify] fold icmp with mul nuw and constant operands
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 5 11:32:30 PDT 2020
Author: Sanjay Patel
Date: 2020-08-05T14:32:17-04:00
New Revision: f879c9b796210d0b2407d022e216cc4d907818a3
URL: https://github.com/llvm/llvm-project/commit/f879c9b796210d0b2407d022e216cc4d907818a3
DIFF: https://github.com/llvm/llvm-project/commit/f879c9b796210d0b2407d022e216cc4d907818a3.diff
LOG: [InstSimplify] fold icmp with mul nuw and constant operands
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.
Added:
Modified:
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/test/Transforms/InstCombine/icmp-mul.ll
llvm/test/Transforms/InstSimplify/icmp-constant.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 148ad21e8015..004d9851edd6 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -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;
}
diff --git a/llvm/test/Transforms/InstCombine/icmp-mul.ll b/llvm/test/Transforms/InstCombine/icmp-mul.ll
index d67181028e45..7f122f59645c 100644
--- a/llvm/test/Transforms/InstCombine/icmp-mul.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-mul.ll
@@ -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
diff --git a/llvm/test/Transforms/InstSimplify/icmp-constant.ll b/llvm/test/Transforms/InstSimplify/icmp-constant.ll
index 7cde4f2488c3..88ffe2b798f7 100644
--- a/llvm/test/Transforms/InstSimplify/icmp-constant.ll
+++ b/llvm/test/Transforms/InstSimplify/icmp-constant.ll
@@ -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
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