[InstCombine] fix operand-complexity-based canonicalization (PR28296)
The code comments didn't match the code logic, and we didn't actually distinguish the fake unary (not/neg/fneg)
operators from arguments. Adding another level to the weighting scheme provides more structure and can help
simplify the pattern matching in InstCombine and other places.
I fixed regressions that would have shown up from this change in:
rL290067
rL290127
But that doesn't mean there are no pattern-matching logic holes left; some combines may just be missing regression tests.
Should fix:
https://llvm.org/bugs/show_bug.cgi?id=28296
Differential Revision: https://reviews.llvm.org/D27933
llvm-svn: 294049
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 9f16a6f..092cc5e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -40,21 +40,29 @@
class MemIntrinsic;
class MemSetInst;
-/// \brief Assign a complexity or rank value to LLVM Values.
+/// Assign a complexity or rank value to LLVM Values. This is used to reduce
+/// the amount of pattern matching needed for compares and commutative
+/// instructions. For example, if we have:
+/// icmp ugt X, Constant
+/// or
+/// xor (add X, Constant), cast Z
+///
+/// We do not have to consider the commuted variants of these patterns because
+/// canonicalization based on complexity guarantees the above ordering.
///
/// This routine maps IR values to various complexity ranks:
/// 0 -> undef
/// 1 -> Constants
/// 2 -> Other non-instructions
/// 3 -> Arguments
-/// 3 -> Unary operations
-/// 4 -> Other instructions
+/// 4 -> Cast and (f)neg/not instructions
+/// 5 -> Other instructions
static inline unsigned getComplexity(Value *V) {
if (isa<Instruction>(V)) {
- if (BinaryOperator::isNeg(V) || BinaryOperator::isFNeg(V) ||
- BinaryOperator::isNot(V))
- return 3;
- return 4;
+ if (isa<CastInst>(V) || BinaryOperator::isNeg(V) ||
+ BinaryOperator::isFNeg(V) || BinaryOperator::isNot(V))
+ return 4;
+ return 5;
}
if (isa<Argument>(V))
return 3;