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InstSimplify: Don't allow (x srem y) urem y -> x srem y

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Let's consider the case where:
%x i16 = 32768
%y i16 = 384

%x srem %y = 65408
(%x srem %y) urem %y = 128

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217939 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-09-17 04:16:35 +00:00
parent 27e656c742
commit d5f73530de
2 changed files with 26 additions and 5 deletions
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8
lib/Analysis/InstructionSimplify.cpp
View File

@ -1171,10 +1171,12 @@ static Value *SimplifyRem(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1,
if (Op0 == Op1)
return Constant::getNullValue(Op0->getType());
// ((X % Y) % Y) -> (X % Y)
if (match(Op0, m_SRem(m_Value(), m_Specific(Op1)))) {
// (X % Y) % Y -> X % Y
if ((Opcode == Instruction::SRem &&
match(Op0, m_SRem(m_Value(), m_Specific(Op1)))) ||
(Opcode == Instruction::URem &&
match(Op0, m_URem(m_Value(), m_Specific(Op1)))))
return Op0;
}
// If the operation is with the result of a select instruction, check whether
// operating on either branch of the select always yields the same value.

23
test/Transforms/InstSimplify/rem.ll
View File

@ -16,11 +16,30 @@ define i32 @select2(i32 %x, i1 %b) {
; CHECK: ret i32 0
}
define i32 @select3(i32 %x, i32 %n) {
; CHECK-LABEL: @select3(
define i32 @rem1(i32 %x, i32 %n) {
; CHECK-LABEL: @rem1(
; CHECK-NEXT: %mod = srem i32 %x, %n
; CHECK-NEXT: ret i32 %mod
%mod = srem i32 %x, %n
%mod1 = srem i32 %mod, %n
ret i32 %mod1
}
define i32 @rem2(i32 %x, i32 %n) {
; CHECK-LABEL: @rem2(
; CHECK-NEXT: %mod = urem i32 %x, %n
; CHECK-NEXT: ret i32 %mod
%mod = urem i32 %x, %n
%mod1 = urem i32 %mod, %n
ret i32 %mod1
}
define i32 @rem3(i32 %x, i32 %n) {
; CHECK-LABEL: @rem3(
; CHECK-NEXT: %[[srem:.*]] = srem i32 %x, %n
; CHECK-NEXT: %[[urem:.*]] = urem i32 %[[srem]], %n
; CHECK-NEXT: ret i32 %[[urem]]
%mod = srem i32 %x, %n
%mod1 = urem i32 %mod, %n
ret i32 %mod1
}