InstCombine: Restrict computeKnownBits() on all Values to OptLevel > 2
As part of r251146 InstCombine was extended to call computeKnownBits on
every value in the function to determine whether it happens to be
constant. This increases typical compiletime by 1-3% (5% in irgen+opt
time) in my measurements. On the other hand this case did not trigger
once in the whole llvm-testsuite.
This patch introduces the notion of ExpensiveCombines which are only
enabled for OptLevel > 2. I removed the check in InstructionSimplify as
that is called from various places where the OptLevel is not known but
given the rarity of the situation I think a check in InstCombine is
enough.
Differential Revision: http://reviews.llvm.org/D16835
llvm-svn: 263047
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index c251683..1909cba 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -177,6 +177,8 @@
private:
// Mode in which we are running the combiner.
const bool MinimizeSize;
+ /// Enable combines that trigger rarely but are costly in compiletime.
+ const bool ExpensiveCombines;
AliasAnalysis *AA;
@@ -195,11 +197,12 @@
public:
InstCombiner(InstCombineWorklist &Worklist, BuilderTy *Builder,
- bool MinimizeSize, AliasAnalysis *AA,
+ bool MinimizeSize, bool ExpensiveCombines, AliasAnalysis *AA,
AssumptionCache *AC, TargetLibraryInfo *TLI,
DominatorTree *DT, const DataLayout &DL, LoopInfo *LI)
: Worklist(Worklist), Builder(Builder), MinimizeSize(MinimizeSize),
- AA(AA), AC(AC), TLI(TLI), DT(DT), DL(DL), LI(LI), MadeIRChange(false) {}
+ ExpensiveCombines(ExpensiveCombines), AA(AA), AC(AC), TLI(TLI), DT(DT),
+ DL(DL), LI(LI), MadeIRChange(false) {}
/// \brief Run the combiner over the entire worklist until it is empty.
///