diff options
Diffstat (limited to 'src/passes/OptimizeInstructions.cpp')
| -rw-r--r-- | src/passes/OptimizeInstructions.cpp | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp index 42d92751f..047ed8551 100644 --- a/src/passes/OptimizeInstructions.cpp +++ b/src/passes/OptimizeInstructions.cpp @@ -2418,6 +2418,26 @@ private: return curr->type == Type::i64 ? builder.makeUnary(ExtendUInt32, c) : c; } } + // Flip the arms if doing so might help later optimizations here. + if (auto* binary = curr->condition->dynCast<Binary>()) { + auto inv = invertBinaryOp(binary->op); + if (inv != InvalidBinary) { + // For invertible binary operations, we prefer to have non-zero values + // in the ifTrue, and zero values in the ifFalse, due to the + // optimization right after us. Even if this does not help there, it is + // a nice canonicalization. (To ensure convergence - that we don't keep + // doing work each time we get here - do nothing if both are zero, or + // if both are nonzero.) + Const* c; + if ((matches(curr->ifTrue, ival(0)) && + !matches(curr->ifFalse, ival(0))) || + (!matches(curr->ifTrue, ival()) && + matches(curr->ifFalse, ival(&c)) && !c->value.isZero())) { + binary->op = inv; + std::swap(curr->ifTrue, curr->ifFalse); + } + } + } if (curr->type == Type::i32 && Bits::getMaxBits(curr->condition, this) <= 1 && Bits::getMaxBits(curr->ifTrue, this) <= 1 && @@ -4168,8 +4188,9 @@ private: } } + // Invert (negate) the opcode, so that it has the exact negative meaning as it + // had before. BinaryOp invertBinaryOp(BinaryOp op) { - // use de-morgan's laws switch (op) { case EqInt32: return NeInt32; @@ -4228,6 +4249,9 @@ private: } } + // Change the opcode so it is correct after reversing the operands. That is, + // we had X OP Y and we need OP' so that this is equivalent to that: + // Y OP' X BinaryOp reverseRelationalOp(BinaryOp op) { switch (op) { case EqInt32: |