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[InstSimplify] Optimize away udivs in the presence of range metadata

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We know that udiv %V, C can be optimized away to 0 if %V is ult C.

llvm-svn: 291296
This commit is contained in:
David Majnemer 2017-01-06 22:58:02 +00:00
parent 8c87177d0b
commit 93fad2f404
2 changed files with 25 additions and 0 deletions
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10
lib/Analysis/InstructionSimplify.cpp
View File

@ -1106,6 +1106,16 @@ static Value *SimplifyUDivInst(Value *Op0, Value *Op1, const Query &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());
}
}
}
return nullptr;
}

15
test/Transforms/InstSimplify/div.ll Normal file
View File

@ -0,0 +1,15 @@
; RUN: opt < %s -instsimplify -S | FileCheck %s
declare i32 @external()
define i32 @div1() {
; CHECK-LABEL: @div1(
; CHECK: [[CALL:%.*]] = call i32 @external(), !range !0
; CHECK-NEXT: ret i32 0
;
%call = call i32 @external(), !range !0
%urem = udiv i32 %call, 3
ret i32 %urem
}
!0 = !{i32 0, i32 3}