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teach the optimizer how to constant fold uadd/usub intrinsics. 

llvm-svn: 83295
This commit is contained in:
Chris Lattner 2009-10-05 05:26:04 +00:00
parent 351534f9b1
commit 59d939894b
2 changed files with 82 additions and 1 deletions
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28
llvm/lib/Analysis/ConstantFolding.cpp
View File

@ -677,6 +677,8 @@ llvm::canConstantFoldCallTo(const Function *F) {
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
case Intrinsic::uadd_with_overflow:
case Intrinsic::usub_with_overflow:
return true;
default:
return false;
@ -881,6 +883,32 @@ llvm::ConstantFoldCall(Function *F,
}
return 0;
}
if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
switch (F->getIntrinsicID()) {
default: break;
case Intrinsic::uadd_with_overflow: {
Constant *Res = ConstantExpr::getAdd(Op1, Op2); // result.
Constant *Ops[] = {
Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
};
return ConstantStruct::get(F->getContext(), Ops, 2, false);
}
case Intrinsic::usub_with_overflow: {
Constant *Res = ConstantExpr::getSub(Op1, Op2); // result.
Constant *Ops[] = {
Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
};
return ConstantStruct::get(F->getContext(), Ops, 2, false);
}
}
}
return 0;
}
return 0;
}
return 0;
}

53
llvm/test/Transforms/ConstProp/overflow-ops.ll Normal file
View File

@ -0,0 +1,53 @@
; RUN: opt < %s -constprop -S | FileCheck %s
%i8i1 = type {i8, i1}
;;-----------------------------
;; uadd
;;-----------------------------
define {i8, i1} @uadd_1() nounwind {
entry:
%t = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 42, i8 100)
ret {i8, i1} %t
; CHECK: @uadd_1
; CHECK: ret %i8i1 { i8 -114, i1 false }
}
define {i8, i1} @uadd_2() nounwind {
entry:
%t = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 142, i8 120)
ret {i8, i1} %t
; CHECK: @uadd_2
; CHECK: ret %i8i1 { i8 6, i1 true }
}
;;-----------------------------
;; usub
;;-----------------------------
define {i8, i1} @usub_1() nounwind {
entry:
%t = call {i8, i1} @llvm.usub.with.overflow.i8(i8 4, i8 2)
ret {i8, i1} %t
; CHECK: @usub_1
; CHECK: ret %i8i1 { i8 2, i1 false }
}
define {i8, i1} @usub_2() nounwind {
entry:
%t = call {i8, i1} @llvm.usub.with.overflow.i8(i8 4, i8 6)
ret {i8, i1} %t
; CHECK: @usub_2
; CHECK: ret %i8i1 { i8 -2, i1 true }
}
declare {i8, i1} @llvm.uadd.with.overflow.i8(i8, i8)
declare {i8, i1} @llvm.usub.with.overflow.i8(i8, i8)