[InstSimplify] fold icmp with mul nsw and constant operands

https://rise4fun.com/Alive/slvl

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

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

Follow-up to the 'nuw' variation added with:
rGf879c9b79621

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 004d985..6683dd2 100644 (file)
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2750,12 +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)
+  // (mul nuw/nsw X, MulC) != C --> true  (if C is not a multiple of MulC)
+  // (mul nuw/nsw 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)
+      ((match(LHS, m_NUWMul(m_Value(), m_APIntAllowUndef(MulC))) &&
+        C->urem(*MulC) != 0) ||
+       (match(LHS, m_NSWMul(m_Value(), m_APIntAllowUndef(MulC))) &&
+        C->srem(*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 7f122f5..24709a2 100644 (file)
--- a/llvm/test/Transforms/InstCombine/icmp-mul.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-mul.ll
@@ -194,9 +194,7 @@ define i1 @ugt_rem_zero_nonuw(i8 %x) {
 
 define i1 @sgt_minnum(i8 %x) {
 ; CHECK-LABEL: @sgt_minnum(
-; CHECK-NEXT:    [[A:%.*]] = mul nsw i8 [[X:%.*]], 7
-; CHECK-NEXT:    [[B:%.*]] = icmp ne i8 [[A]], -128
-; CHECK-NEXT:    ret i1 [[B]]
+; CHECK-NEXT:    ret i1 true
 ;
   %a = mul nsw i8 %x, 7
   %b = icmp sgt i8 %a, -128

diff --git a/llvm/test/Transforms/InstSimplify/icmp-constant.ll b/llvm/test/Transforms/InstSimplify/icmp-constant.ll
index 88ffe2b..e8d2a4b 100644 (file)
--- a/llvm/test/Transforms/InstSimplify/icmp-constant.ll
+++ b/llvm/test/Transforms/InstSimplify/icmp-constant.ll
@@ -916,3 +916,110 @@ define i1 @mul_nuw_urem_cmp_neg_constant_is_0(i8 %x) {
   %r = icmp eq i8 %m, -127
   ret i1 %r
 }
+
+; No overflow, so mul constant must be a factor of cmp constant.
+
+define i1 @mul_nsw_srem_cmp_constant1(i8 %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_constant1(
+; CHECK-NEXT:    ret i1 false
+;
+  %m = mul nsw i8 %x, 43
+  %r = icmp eq i8 %m, 45
+  ret i1 %r
+}
+
+; Invert predicate and check vector type.
+
+define <2 x i1> @mul_nsw_srem_cmp_constant_vec_splat(<2 x i8> %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_constant_vec_splat(
+; CHECK-NEXT:    ret <2 x i1> <i1 true, i1 true>
+;
+  %m = mul nsw <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_nsw_srem_cmp_constant_vec_splat_undef1(<2 x i8> %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_constant_vec_splat_undef1(
+; CHECK-NEXT:    ret <2 x i1> <i1 true, i1 true>
+;
+  %m = mul nsw <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_nsw_srem_cmp_constant_vec_splat_undef2(<2 x i8> %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_constant_vec_splat_undef2(
+; CHECK-NEXT:    ret <2 x i1> <i1 true, i1 true>
+;
+  %m = mul nsw <2 x i8> %x, <i8 undef, i8 45>
+  %r = icmp ne <2 x i8> %m, <i8 15, i8 15>
+  ret <2 x i1> %r
+}
+
+; Check negative numbers (constants should be analyzed as signed).
+
+define i1 @mul_nsw_srem_cmp_constant2(i8 %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_constant2(
+; CHECK-NEXT:    ret i1 false
+;
+  %m = mul nsw i8 %x, 43
+  %r = icmp eq i8 %m, -127
+  ret i1 %r
+}
+
+; Negative test - require nsw.
+
+define i1 @mul_srem_cmp_constant1(i8 %x) {
+; CHECK-LABEL: @mul_srem_cmp_constant1(
+; CHECK-NEXT:    [[M:%.*]] = mul i8 [[X:%.*]], 43
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[M]], 42
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %m = mul i8 %x, 43
+  %r = icmp eq i8 %m, 42
+  ret i1 %r
+}
+
+; Negative test - x could be 0.
+
+define i1 @mul_nsw_srem_cmp_constant0(i8 %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_constant0(
+; CHECK-NEXT:    [[M:%.*]] = mul nsw i8 [[X:%.*]], 23
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[M]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %m = mul nsw i8 %x, 23
+  %r = icmp eq i8 %m, 0
+  ret i1 %r
+}
+
+; Negative test - cmp constant is multiple of mul constant.
+
+define i1 @mul_nsw_srem_cmp_constant_is_0(i8 %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_constant_is_0(
+; CHECK-NEXT:    [[M:%.*]] = mul nsw i8 [[X:%.*]], 42
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[M]], 84
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %m = mul nsw i8 %x, 42
+  %r = icmp eq i8 %m, 84
+  ret i1 %r
+}
+
+; Negative test - cmp constant is multiple (treated as signed).
+
+define i1 @mul_nsw_srem_cmp_neg_constant_is_0(i8 %x) {
+; CHECK-LABEL: @mul_nsw_srem_cmp_neg_constant_is_0(
+; CHECK-NEXT:    [[M:%.*]] = mul nsw i8 [[X:%.*]], -42
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[M]], -84
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %m = mul nsw i8 %x, -42
+  %r = icmp eq i8 %m, -84
+  ret i1 %r
+}