OptimizeInstruction: Optimize any boolean & (No overlap with boolean's LSB) ==> 0 #7505
Conversation
| uint64_t constantValue = c->value.getInteger(); | ||
| if ((constantValue & mask) == 0) { | ||
| replaceCurrent(getDroppedChildrenAndAppend( | ||
| curr, LiteralUtils::makeZero(type, *getModule()))); |
There was a problem hiding this comment.
For both the replaceCurrent() calls in this function, the caller does that on the returned value, so we can just return the value here.
| auto* right = curr->right; | ||
| auto leftMaxBits = Bits::getMaxBits(left, this); | ||
|
|
||
| if (leftMaxBits == 0) { |
There was a problem hiding this comment.
Does 0 need to be special-cased? I think it can work without it (if not, a comment would help).
There was a problem hiding this comment.
Oh, also, the case of 0 & .. should already be handled elsewhere, so we don't need to handle it here anyhow
| ;; CHECK-NEXT: (i32.and | ||
| ;; CHECK-NEXT: (i32.const 1) | ||
| ;; CHECK-NEXT: (i32.const 2) | ||
| ;; CHECK-NEXT: ) |
There was a problem hiding this comment.
The goal of this existing test is to see the order of the operands, so this optimization prevents the test from working. To avoid that, the test can be modified to check two different numbers, perhaps (does 2, 1 - reversing the order - work perhaps?)
| ;; CHECK-NEXT: (i32.const 127) | ||
| ;; CHECK-NEXT: (i32.const 128) | ||
| ;; CHECK-NEXT: ) | ||
| ;; CHECK-NEXT: (i32.const 0) | ||
| ;; CHECK-NEXT: ) | ||
| (func $sext-24-and-127-128 (result i32) | ||
| (i32.shr_s |
There was a problem hiding this comment.
The goal in this test is to see that the sign-extend can be removed. If it optimizes all the way to 0, that isn't clear. Perhaps the constant 128 a few lines below can be replaced with a local.get, so it is unknown?
| ;; CHECK-NEXT: (local.get $x) | ||
| ;; CHECK-NEXT: ) | ||
| ;; CHECK-NEXT: (i32.const 2) | ||
| ;; CHECK-NEXT: ) |
There was a problem hiding this comment.
Perhaps the i64 2 could be an i64 param, to avoid this getting optimized away.
| ;; CHECK-NEXT: ) | ||
| ;; CHECK-NEXT: (i32.const 2) | ||
| ;; CHECK-NEXT: ) | ||
| ;; CHECK-NEXT: (i32.const 0) | ||
| ;; CHECK-NEXT: ) | ||
| ;; CHECK-NEXT: (drop | ||
| ;; CHECK-NEXT: (i32.eqz |
There was a problem hiding this comment.
We will need new tests for the new function optimizeAndNoOverlappingBits, including the various corner cases (just one overlapping bit, no overlapping bits, etc.)
There are so many rules for
and, but we still cannot optimize the following one:to zero.
Adding rule for
add:any boolean & (No overlap with boolean's LSB) ==> 0Fixes: #7481