maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[ValueTracking] Early exit when further analysis won't be fruitful. 

This should have NFC in the context of codegen, but may have positive
implications on compile-time.

llvm-svn: 268651
This commit is contained in:
Chad Rosier 2016-05-05 17:41:19 +00:00
parent ffbd56a1c9
commit 226a734f1a
1 changed files with 32 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -3922,19 +3922,24 @@ isImpliedCondOperands(CmpInst::Predicate Pred, Value *ALHS, Value *ARHS,
}
}
/// Return true if the operands of the two compares match. IsSwappedOps is true
/// when the operands match, but are swapped.
static bool isMatchingOps(Value *ALHS, Value *ARHS, Value *BLHS, Value *BRHS,
bool &IsSwappedOps) {
bool IsMatchingOps = (ALHS == BLHS && ARHS == BRHS);
IsSwappedOps = (ALHS == BRHS && ARHS == BLHS);
return IsMatchingOps || IsSwappedOps;
}
/// Return true if "icmp1 APred ALHS ARHS" implies "icmp2 BPred BLHS BRHS" is
/// true. Return false if "icmp1 APred ALHS ARHS" implies "icmp2 BPred BLHS
/// BRHS" is false. Otherwise, return None if we can't infer anything.
static Optional<bool> isImpliedCondMatchingOperands(CmpInst::Predicate APred,
Value *ALHS, Value *ARHS,
CmpInst::Predicate BPred,
Value *BLHS, Value *BRHS) {
// The operands of the two compares must match.
bool IsMatchingOps = (ALHS == BLHS && ARHS == BRHS);
bool IsSwappedOps = (ALHS == BRHS && ARHS == BLHS);
if (!IsMatchingOps && !IsSwappedOps)
return None;
Value *BLHS, Value *BRHS,
bool IsSwappedOps) {
// Canonicalize the operands so they're matching.
if (IsSwappedOps) {
std::swap(BLHS, BRHS);
@ -4001,17 +4006,27 @@ Optional<bool> llvm::isImpliedCondition(Value *LHS, Value *RHS,
if (InvertAPred)
APred = CmpInst::getInversePredicate(APred);
Optional<bool> Implication =
isImpliedCondMatchingOperands(APred, ALHS, ARHS, BPred, BLHS, BRHS);
if (Implication)
return Implication;
if (ALHS == BLHS && isa<ConstantInt>(ARHS) && isa<ConstantInt>(BRHS)) {
Implication =
isImpliedCondMatchingImmOperands(APred, ALHS, cast<ConstantInt>(ARHS),
BPred, BLHS, cast<ConstantInt>(BRHS));
if (Implication)
// Can we infer anything when the two compares have matching operands?
bool IsSwappedOps;
if (isMatchingOps(ALHS, ARHS, BLHS, BRHS, IsSwappedOps)) {
if (Optional<bool> Implication = isImpliedCondMatchingOperands(
APred, ALHS, ARHS, BPred, BLHS, BRHS, IsSwappedOps))
return Implication;
// No amount of additional analysis will infer the second condition, so
// early exit.
return None;
}
// Can we infer anything when the LHS operands match and the RHS operands are
// constants (not necessarily matching)?
if (ALHS == BLHS && isa<ConstantInt>(ARHS) && isa<ConstantInt>(BRHS)) {
if (Optional<bool> Implication = isImpliedCondMatchingImmOperands(
APred, ALHS, cast<ConstantInt>(ARHS), BPred, BLHS,
cast<ConstantInt>(BRHS)))
return Implication;
// No amount of additional analysis will infer the second condition, so
// early exit.
return None;
}
if (APred == BPred)