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-rw-r--r--llvm/lib/Analysis/InstructionSimplify.cpp49
-rw-r--r--llvm/test/Transforms/InstSimplify/div.ll68
-rw-r--r--llvm/test/Transforms/InstSimplify/rem.ll69
3 files changed, 168 insertions, 18 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 0fb0b7d2449..dbcc7e13f21 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1075,6 +1075,33 @@ Value *llvm::SimplifySDivInst(Value *Op0, Value *Op1, const SimplifyQuery &Q) {
return ::SimplifySDivInst(Op0, Op1, Q, RecursionLimit);
}
+/// Given a predicate and two operands, return true if the comparison is true.
+/// This is a helper for div/rem simplification where we return some other value
+/// when we can prove a relationship between the operands.
+static bool isICmpTrue(ICmpInst::Predicate Pred, Value *LHS, Value *RHS,
+ const SimplifyQuery &Q, unsigned MaxRecurse) {
+ Value *V = SimplifyICmpInst(Pred, LHS, RHS, Q, MaxRecurse);
+ Constant *C = dyn_cast_or_null<Constant>(V);
+ return (C && C->isAllOnesValue());
+}
+
+static Value *simplifyUnsignedDivRem(Value *Op0, Value *Op1,
+ const SimplifyQuery &Q,
+ unsigned MaxRecurse, bool IsDiv) {
+ // Recursion is always used, so bail out at once if we already hit the limit.
+ if (!MaxRecurse--)
+ return nullptr;
+
+ // If we can prove that the quotient is unsigned less than the divisor, then
+ // we know the answer:
+ // X / Y --> 0
+ // X % Y --> X
+ if (isICmpTrue(ICmpInst::ICMP_ULT, Op0, Op1, Q, MaxRecurse))
+ return IsDiv ? Constant::getNullValue(Op0->getType()) : Op0;
+
+ return nullptr;
+}
+
/// Given operands for a UDiv, see if we can fold the result.
/// If not, this returns null.
static Value *SimplifyUDivInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
@@ -1082,15 +1109,8 @@ static Value *SimplifyUDivInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
if (Value *V = SimplifyDiv(Instruction::UDiv, Op0, Op1, Q, MaxRecurse))
return V;
- // udiv %V, C -> 0 if %V < C
- if (MaxRecurse) {
- if (Constant *C = dyn_cast_or_null<Constant>(SimplifyICmpInst(
- ICmpInst::ICMP_ULT, Op0, Op1, Q, MaxRecurse - 1))) {
- if (C->isAllOnesValue()) {
- return Constant::getNullValue(Op0->getType());
- }
- }
- }
+ if (Value *V = simplifyUnsignedDivRem(Op0, Op1, Q, MaxRecurse, true))
+ return V;
return nullptr;
}
@@ -1198,15 +1218,8 @@ static Value *SimplifyURemInst(Value *Op0, Value *Op1, const SimplifyQuery &Q,
if (Value *V = SimplifyRem(Instruction::URem, Op0, Op1, Q, MaxRecurse))
return V;
- // urem %V, C -> %V if %V < C
- if (MaxRecurse) {
- if (Constant *C = dyn_cast_or_null<Constant>(SimplifyICmpInst(
- ICmpInst::ICMP_ULT, Op0, Op1, Q, MaxRecurse - 1))) {
- if (C->isAllOnesValue()) {
- return Op0;
- }
- }
- }
+ if (Value *V = simplifyUnsignedDivRem(Op0, Op1, Q, MaxRecurse, false))
+ return V;
return nullptr;
}
diff --git a/llvm/test/Transforms/InstSimplify/div.ll b/llvm/test/Transforms/InstSimplify/div.ll
index f096719359d..be17746c24f 100644
--- a/llvm/test/Transforms/InstSimplify/div.ll
+++ b/llvm/test/Transforms/InstSimplify/div.ll
@@ -54,6 +54,74 @@ define <2 x i1> @udiv_bool_vec(<2 x i1> %x, <2 x i1> %y) {
ret <2 x i1> %div
}
+define i32 @udiv_quotient_known_smaller_than_constant_denom(i32 %x) {
+; CHECK-LABEL: @udiv_quotient_known_smaller_than_constant_denom(
+; CHECK-NEXT: ret i32 0
+;
+ %and = and i32 %x, 250
+ %div = udiv i32 %and, 251
+ ret i32 %div
+}
+
+define i32 @not_udiv_quotient_known_smaller_than_constant_denom(i32 %x) {
+; CHECK-LABEL: @not_udiv_quotient_known_smaller_than_constant_denom(
+; CHECK-NEXT: [[AND:%.*]] = and i32 %x, 251
+; CHECK-NEXT: [[DIV:%.*]] = udiv i32 [[AND]], 251
+; CHECK-NEXT: ret i32 [[DIV]]
+;
+ %and = and i32 %x, 251
+ %div = udiv i32 %and, 251
+ ret i32 %div
+}
+
+define i32 @udiv_constant_quotient_known_smaller_than_denom(i32 %x) {
+; CHECK-LABEL: @udiv_constant_quotient_known_smaller_than_denom(
+; CHECK-NEXT: ret i32 0
+;
+ %or = or i32 %x, 251
+ %div = udiv i32 250, %or
+ ret i32 %div
+}
+
+define i32 @not_udiv_constant_quotient_known_smaller_than_denom(i32 %x) {
+; CHECK-LABEL: @not_udiv_constant_quotient_known_smaller_than_denom(
+; CHECK-NEXT: [[OR:%.*]] = or i32 %x, 251
+; CHECK-NEXT: [[DIV:%.*]] = udiv i32 251, [[OR]]
+; CHECK-NEXT: ret i32 [[DIV]]
+;
+ %or = or i32 %x, 251
+ %div = udiv i32 251, %or
+ ret i32 %div
+}
+
+; This would require computing known bits on both x and y. Is it worth doing?
+
+define i32 @udiv_quotient_known_smaller_than_denom(i32 %x, i32 %y) {
+; CHECK-LABEL: @udiv_quotient_known_smaller_than_denom(
+; CHECK-NEXT: [[AND:%.*]] = and i32 %x, 250
+; CHECK-NEXT: [[OR:%.*]] = or i32 %y, 251
+; CHECK-NEXT: [[DIV:%.*]] = udiv i32 [[AND]], [[OR]]
+; CHECK-NEXT: ret i32 [[DIV]]
+;
+ %and = and i32 %x, 250
+ %or = or i32 %y, 251
+ %div = udiv i32 %and, %or
+ ret i32 %div
+}
+
+define i32 @not_udiv_quotient_known_smaller_than_denom(i32 %x, i32 %y) {
+; CHECK-LABEL: @not_udiv_quotient_known_smaller_than_denom(
+; CHECK-NEXT: [[AND:%.*]] = and i32 %x, 251
+; CHECK-NEXT: [[OR:%.*]] = or i32 %y, 251
+; CHECK-NEXT: [[DIV:%.*]] = udiv i32 [[AND]], [[OR]]
+; CHECK-NEXT: ret i32 [[DIV]]
+;
+ %and = and i32 %x, 251
+ %or = or i32 %y, 251
+ %div = udiv i32 %and, %or
+ ret i32 %div
+}
+
declare i32 @external()
define i32 @div1() {
diff --git a/llvm/test/Transforms/InstSimplify/rem.ll b/llvm/test/Transforms/InstSimplify/rem.ll
index b7f18f36b4b..05818043bc1 100644
--- a/llvm/test/Transforms/InstSimplify/rem.ll
+++ b/llvm/test/Transforms/InstSimplify/rem.ll
@@ -104,6 +104,75 @@ define i32 @rem3(i32 %x, i32 %n) {
ret i32 %mod1
}
+define i32 @urem_quotient_known_smaller_than_constant_denom(i32 %x) {
+; CHECK-LABEL: @urem_quotient_known_smaller_than_constant_denom(
+; CHECK-NEXT: [[AND:%.*]] = and i32 %x, 250
+; CHECK-NEXT: ret i32 [[AND]]
+;
+ %and = and i32 %x, 250
+ %r = urem i32 %and, 251
+ ret i32 %r
+}
+
+define i32 @not_urem_quotient_known_smaller_than_constant_denom(i32 %x) {
+; CHECK-LABEL: @not_urem_quotient_known_smaller_than_constant_denom(
+; CHECK-NEXT: [[AND:%.*]] = and i32 %x, 251
+; CHECK-NEXT: [[R:%.*]] = urem i32 [[AND]], 251
+; CHECK-NEXT: ret i32 [[R]]
+;
+ %and = and i32 %x, 251
+ %r = urem i32 %and, 251
+ ret i32 %r
+}
+
+define i32 @urem_constant_quotient_known_smaller_than_denom(i32 %x) {
+; CHECK-LABEL: @urem_constant_quotient_known_smaller_than_denom(
+; CHECK-NEXT: ret i32 250
+;
+ %or = or i32 %x, 251
+ %r = urem i32 250, %or
+ ret i32 %r
+}
+
+define i32 @not_urem_constant_quotient_known_smaller_than_denom(i32 %x) {
+; CHECK-LABEL: @not_urem_constant_quotient_known_smaller_than_denom(
+; CHECK-NEXT: [[OR:%.*]] = or i32 %x, 251
+; CHECK-NEXT: [[R:%.*]] = urem i32 251, [[OR]]
+; CHECK-NEXT: ret i32 [[R]]
+;
+ %or = or i32 %x, 251
+ %r = urem i32 251, %or
+ ret i32 %r
+}
+
+; This would require computing known bits on both x and y. Is it worth doing?
+
+define i32 @urem_quotient_known_smaller_than_denom(i32 %x, i32 %y) {
+; CHECK-LABEL: @urem_quotient_known_smaller_than_denom(
+; CHECK-NEXT: [[AND:%.*]] = and i32 %x, 250
+; CHECK-NEXT: [[OR:%.*]] = or i32 %y, 251
+; CHECK-NEXT: [[R:%.*]] = urem i32 [[AND]], [[OR]]
+; CHECK-NEXT: ret i32 [[R]]
+;
+ %and = and i32 %x, 250
+ %or = or i32 %y, 251
+ %r = urem i32 %and, %or
+ ret i32 %r
+}
+
+define i32 @not_urem_quotient_known_smaller_than_denom(i32 %x, i32 %y) {
+; CHECK-LABEL: @not_urem_quotient_known_smaller_than_denom(
+; CHECK-NEXT: [[AND:%.*]] = and i32 %x, 251
+; CHECK-NEXT: [[OR:%.*]] = or i32 %y, 251
+; CHECK-NEXT: [[R:%.*]] = urem i32 [[AND]], [[OR]]
+; CHECK-NEXT: ret i32 [[R]]
+;
+ %and = and i32 %x, 251
+ %or = or i32 %y, 251
+ %r = urem i32 %and, %or
+ ret i32 %r
+}
+
declare i32 @external()
define i32 @rem4() {
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