JIT: Assertprop improvements #97908
JIT: Assertprop improvements #97908
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue DetailsThis PR does:
static int Test(int x)
{
if ((uint)x < 100)
return x % 8;
return 0;
}Codegen diff: ; Method Program:Test(int):int (FullOpts)
G_M46009_IG01:
G_M46009_IG02:
xor eax, eax
mov edx, ecx
- sar edx, 31
and edx, 7
- add edx, ecx
- and edx, -8
- mov r8d, ecx
- sub r8d, edx
cmp ecx, 100
- cmovb eax, r8d
+ cmovb eax, edx
G_M46009_IG03:
ret
-; Total bytes of code: 29
+; Total bytes of code: 14
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PTAL @AndyAyersMS @jakobbotsch @dotnet/jit-contrib |
| // Note this tracks at most only 256 assertions. | ||
| // | ||
| static const AssertionIndex countFunc[] = {64, 128, 256, 64}; | ||
| static const AssertionIndex countFunc[] = {64, 128, 256, 128, 64}; |
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Allowed a bit more assertions for large methods - it was done mainly to fix asm regressions introduced by new asserts where old ones were thrown away due to this limit.
| // Cases where op1 holds the upper bound arithmetic and op2 is 0. | ||
| // Loop condition like: "i < bnd +/-k == 0" | ||
| // Assertion: "i < bnd +/- k == 0" | ||
| if (hasTestAgainstZero && vnStore->IsVNCompareCheckedBoundArith(op1VN)) |
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testAgainstZero asserts have no diffs (x relop y) ==/!= 0. All asserts are just x relop y.
So I removed them.
| { | ||
| // (uint)index < CNS | ||
| // (uint)index >= CNS | ||
| return (funcApp.m_func == VNF_LT_UN) || (funcApp.m_func == VNF_GE_UN); |
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IsVNConstantBoundUnsigned was a bit conservative and only tried to detect useful cases. But it forgot that we create complimentary asserts as well which may turn useless ones into useful too.
| // OAK_[NOT]_EQUAL assertion with op1 being O1K_CONSTANT_LOOP_BND | ||
| // representing "(X relop CNS) ==/!= 0" assertion. | ||
| if (!curAssertion->IsConstantBound()) | ||
| if (!curAssertion->IsConstantBound() && !curAssertion->IsConstantBoundUnsigned()) |
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Here for optAssertionProp_ModDiv I added IsConstantBoundUnsigned (unsigned comparisons against constants).
Previously we could optimize div only for x > cns assert. This adds (uint)x < cns case as well.
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Btw, just FYI: Diffs if we bump max assertions threshold to just 256. |
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/azp run Fuzzlyn |
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Azure Pipelines successfully started running 1 pipeline(s). |
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CI Failure is known |
This PR does:
Codegen diff:
; Method Program:Test(int):int (FullOpts) G_M46009_IG01: G_M46009_IG02: xor eax, eax mov edx, ecx - sar edx, 31 and edx, 7 - add edx, ecx - and edx, -8 - mov r8d, ecx - sub r8d, edx cmp ecx, 100 - cmovb eax, r8d + cmovb eax, edx G_M46009_IG03: ret -; Total bytes of code: 29 +; Total bytes of code: 14