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[InlineCost] Do not take INT_MAX when Cost is negative 

Summary: visitSwitchInst should not take INT_MAX when Cost is negative. Instead of INT_MAX , we also use a valid upperbound cost when overflow occurs in Cost.

Reviewers: hans, echristo, dmgreen

Reviewed By: dmgreen

Subscribers: mcrosier, javed.absar, llvm-commits, eraman

Differential Revision: https://reviews.llvm.org/D34436

llvm-svn: 306118
This commit is contained in:
Jun Bum Lim 2017-06-23 16:12:37 +00:00
parent eaf0051ba3
commit 506cfb7ab7
2 changed files with 48 additions and 5 deletions
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16
llvm/lib/Analysis/InlineCost.cpp
View File

@ -1022,12 +1022,15 @@ bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
// inlining those. It will prevent inlining in cases where the optimization
// does not (yet) fire.
// Maximum valid cost increased in this function.
int CostUpperBound = INT_MAX - InlineConstants::InstrCost - 1;
// Exit early for a large switch, assuming one case needs at least one
// instruction.
// FIXME: This is not true for a bit test, but ignore such case for now to
// save compile-time.
int64_t CostLowerBound =
std::min((int64_t)INT_MAX,
std::min((int64_t)CostUpperBound,
(int64_t)SI.getNumCases() * InlineConstants::InstrCost + Cost);
if (CostLowerBound > Threshold) {
@ -1044,7 +1047,8 @@ bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
if (JumpTableSize) {
int64_t JTCost = (int64_t)JumpTableSize * InlineConstants::InstrCost +
4 * InlineConstants::InstrCost;
Cost = std::min((int64_t)INT_MAX, JTCost + Cost);
Cost = std::min((int64_t)CostUpperBound, JTCost + Cost);
return false;
}
@ -1068,10 +1072,12 @@ bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
Cost += NumCaseCluster * 2 * InlineConstants::InstrCost;
return false;
}
int64_t ExpectedNumberOfCompare = 3 * (uint64_t)NumCaseCluster / 2 - 1;
uint64_t SwitchCost =
int64_t ExpectedNumberOfCompare = 3 * (int64_t)NumCaseCluster / 2 - 1;
int64_t SwitchCost =
ExpectedNumberOfCompare * 2 * InlineConstants::InstrCost;
Cost = std::min((uint64_t)INT_MAX, SwitchCost + Cost);
Cost = std::min((int64_t)CostUpperBound, SwitchCost + Cost);
return false;
}

37
llvm/test/Transforms/Inline/AArch64/switch.ll
View File

@ -121,3 +121,40 @@ define i32 @caller_jumptable(i32 %a, i32 %b, i32* %P) {
ret i32 %r
}
define internal i32 @callee_negativeCost(i32 %t) {
entry:
switch i32 %t, label %sw.default [
i32 1, label %sw.bb
i32 0, label %sw.bb1
i32 42, label %sw.bb2
i32 43, label %sw.bb3
]
sw.bb: ; preds = %entry
br label %cleanup
sw.bb1: ; preds = %entry
br label %cleanup
sw.bb2: ; preds = %entry
br label %cleanup
sw.bb3: ; preds = %entry
br label %cleanup
sw.default: ; preds = %entry
br label %cleanup
cleanup: ; preds = %sw.default, %sw.bb3, %sw.bb2, %sw.bb1, %sw.bb
%retval.0 = phi i32 [ 1, %sw.default ], [ 3, %sw.bb3 ], [ 2, %sw.bb2 ], [ 0, %sw.bb1 ], [ 0, %sw.bb ]
ret i32 %retval.0
}
define i32 @caller_negativeCost(i32 %t) {
; CHECK-LABEL: @caller_negativeCost(
; CHECK-NOT: call i32 @callee_negativeCost
entry:
%call = call i32 @callee_negativeCost(i32 %t)
ret i32 %call
}