Chained comparison of two integers against a constant is not coalesced #102103

pedrobsaila · 2024-05-10T23:24:33Z

neon-sunset · 2024-05-11T12:03:44Z

Seems to have regressions on arm64 too 😢 I suppose Clang/LLVM reasons about these in a more generalized way...

612735.dasm - Program:InstanceMethodTest():ubyte (FullOpts)
@@ -174,11 +174,14 @@ G_M34320_IG08:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref
             ldr     x3, [x3]
             blr     x3
             ; gcrRegs -[x1-x2 x22]
-            cmn     w20, #1
+            movn    w0, #41
+            eor     w0, w21, w0
+            movn    w1, #0
+            eor     w1, w20, w1
+            orr     w0, w0, w1
+            cmp     w0, #0
             cset    x0, eq
-            cmn     w21, #42
-            csel    w0, wzr, w0, ne
-						;; size=88 bbWeight=1 PerfScore 16.00
+						;; size=100 bbWeight=1 PerfScore 17.50

pedrobsaila · 2024-05-12T22:03:14Z

It seems the regressions happen on ARM because it already supports conditional select in assembly which prevents from creating branches. Our optimization seems to confuse the JIT from recognizing the pattern and using the csel in certain methods.

JulieLeeMSFT · 2024-06-17T18:49:24Z

@TIHan, please review this community PR.

jakobbotsch · 2024-07-01T08:30:30Z

/azp run runtime-coreclr superpmi-diffs

azure-pipelines · 2024-07-01T08:30:49Z

Azure Pipelines successfully started running 1 pipeline(s).

jakobbotsch · 2024-07-01T08:31:57Z

src/coreclr/jit/optimizebools.cpp

+#if defined(TARGET_ARM) || defined(TARGET_ARM64)
+    return false;
+#endif


Why this check? There should be a comment why the transformation isn't profitable on these platforms.

@pedrobsaila as well..

The JIT already supports creating conditional chains. It was implemented by @a74nh in #79283. It is only enabled on arm64 because only arm64 has conditional compare.

Conditional compare is going to be better than the xor pattern from the example, that's probably why this is a regression on arm64. Also, x64/x86 is getting conditional compare as part of Intel APX, so it is expected that we will enable the same logic for x86/x64 in the future. Given this and the small diffs of this PR I'm not sure the complexity is warranted.

If we want to have this transformation then it should be done by enabling optOptimizeCompareChainCondBlock for x86/x64. Then the backend should be taught how to translate this pattern to something more profitable on x86/x64. Currently it only knows how to do that for arm64. The transformation is done by TryLowerAndOrToCCMP. x86/x64 should have a similar version that is translated by using xor instead. Most likely optOptimizeCompareChainCondBlock will have to be restricted on the patterns it allows to combine on x86/x64 since there is no true conditional compare yet.

(I removed my comment because I misread this feedback as asking the author rather than a nudge to provide context on disabling on ARM64, though I was hoping to see much larger amount of diffs - this pattern is pretty common after all)

Indeed ccmp is emitted by both Clang and GCC: https://godbolt.org/z/srhqPrK4v

Why this check?

yes the ARM support for branchless conditional select is what motivated the if, the xor pattern ends up being more expensive in this case.

If we want to have this transformation then it should be done by enabling optOptimizeCompareChainCondBlock for x86/x64

If I do understand the code well, this would optimize comparison checks for conditional blocks but not for return ones. Do I need to delete the optimization for the latest ?

I think it's ok to add some handling for return blocks if the existing handling doesn't cover it. But I think you should transform it into bitwise ops (i.e. return (x == 0x80) && (y == 0x80) => return (x == 0x80) & (y == 0x80) so that the remaining handling falls out naturally from TryLowerAndOrToCCMP (and the x64 specific variant being introduced).

pedrobsaila · 2024-08-28T19:56:58Z

Sorry for the delay @jakobbotsch, it took me sometime to figure it out. Can you reopen my PR ?

a74nh · 2024-09-02T09:56:52Z

src/coreclr/jit/optimizebools.cpp

@@ -421,7 +424,10 @@ bool OptBoolsDsc::FindCompareChain(GenTree* condition, bool* isTestCondition)
            *isTestCondition = true;
        }
        else if (condOp1->OperIs(GT_AND) && isPow2(static_cast<target_size_t>(condOp2Value)) &&
-                 condOp1->gtGetOp2()->IsIntegralConst(condOp2Value))


Why can't IsIntegralConst() be used here? It looks the same to me.

a74nh · 2024-09-02T10:01:20Z

I'm assuming this PR has no code diffs on Arm64?

jakobbotsch · 2024-09-02T10:10:24Z

src/coreclr/jit/lowerxarch.cpp

+    if (!lastNode->OperIs(GT_JTRUE, GT_RETURN))
+    {
+        return false;
+    }


This does not make sense to me. This transformation should be beneficial to do regardless of how the and/or is used.

jakobbotsch · 2024-09-02T10:15:42Z

src/coreclr/jit/lowerxarch.cpp

+    if (!op1->OperIs(GT_NE, GT_EQ) || !op2->OperIs(GT_NE, GT_EQ) ||
+        (lastNode->OperIs(GT_JTRUE) && ((tree->OperIs(GT_OR) && (!op1->OperIs(GT_NE) || !op2->OperIs(GT_NE))) ||
+                                        (tree->OperIs(GT_AND) && (!op1->OperIs(GT_EQ) || !op2->OperIs(GT_EQ))))) ||
+        (lastNode->OperIs(GT_RETURN) && ((tree->OperIs(GT_OR) && (!op1->OperIs(GT_EQ) || !op2->OperIs(GT_EQ))) ||
+                                         (tree->OperIs(GT_AND) && (!op1->OperIs(GT_NE) || !op2->OperIs(GT_NE))))))
+    {
+        return false;
+    }


Here too the JTRUE/RETURN checks do not make sense to me. Imagine having

bool foo = (x == 0) & (y == 0). bool bar = (x != 0) | (y != 0);

in any basic block. The transformation should be able to kick in for this pattern regardless of what type of basic block it appears in.

dotnet-policy-service · 2024-10-21T16:50:41Z

This pull request has been automatically marked no-recent-activity because it has not had any activity for 14 days. It will be closed if no further activity occurs within 14 more days. Any new comment (by anyone, not necessarily the author) will remove no-recent-activity.

dotnet-policy-service · 2024-11-04T18:38:04Z

This pull request will now be closed since it had been marked no-recent-activity but received no further activity in the past 14 days. It is still possible to reopen or comment on the pull request, but please note that it will be locked if it remains inactive for another 30 days.

Chained comparison of two integers against a constant is not coalesced

43dad09

dotnet-issue-labeler bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label May 10, 2024

dotnet-policy-service bot added the community-contribution Indicates that the PR has been added by a community member label May 10, 2024

format file

951ce9d

pedrobsaila added 2 commits May 11, 2024 23:05

optimize only int operands

a8dbdbf

try to fix segmentation fault on arm

64a79f5

This was referenced May 12, 2024

Test failure WindowsAlternateDataStreamOverwrite #83659

Open

slow macOS - "##[error]The job running on agent Azure Pipelines 9 ran longer than the maximum time of 60 minutes." dotnet/dnceng#1883

Open

Dead lettering tests #101524

Closed

pedrobsaila closed this May 12, 2024

pedrobsaila reopened this May 12, 2024

build-analysis bot mentioned this pull request May 12, 2024

Test failure in System.Numerics.Tensors.Tests.SingleGenericTensorPrimitives.SpanDestinationFunctions_SpecialValues #101731

Closed

pedrobsaila added 2 commits May 12, 2024 15:23

try fix errors in arm builds

34c6eb7

fix regression on pattern a != || b==

4f37008

pedrobsaila added 2 commits May 13, 2024 22:36

Merge remote-tracking branch 'upstream/main' into 101347

872a62e

do not optimize for arm

5591e9a

JulieLeeMSFT requested a review from TIHan June 17, 2024 18:48

jakobbotsch reviewed Jul 1, 2024

View reviewed changes

Merge remote-tracking branch 'upstream/main' into 101347

5fbaa7d

JulieLeeMSFT assigned pedrobsaila Jul 9, 2024

JulieLeeMSFT added the needs-author-action An issue or pull request that requires more info or actions from the author. label Jul 9, 2024

Merge remote-tracking branch 'upstream/main' into 101347

62e5261

dotnet-policy-service bot added the no-recent-activity label Jul 26, 2024

dotnet-policy-service bot closed this Aug 9, 2024

Merge remote-tracking branch 'upstream/main' into 101347

99bd794

pedrobsaila added 5 commits August 19, 2024 23:12

rollback dev

c653261

rollback test

f6b4e8a

Merge remote-tracking branch 'upstream/main' into 101347

dec1c11

fix remarks

0bfee18

Merge remote-tracking branch 'upstream/main' into 101347

679bfec

jakobbotsch reopened this Aug 28, 2024

dotnet-policy-service bot removed no-recent-activity needs-author-action An issue or pull request that requires more info or actions from the author. labels Aug 28, 2024

pedrobsaila added 2 commits August 28, 2024 23:12

fix build errors 1

e24840d

fix build errors 2

781c223

build-analysis bot mentioned this pull request Aug 29, 2024

3 System.Diagnostics tests failing - System.FormatException : The input is not a valid Base-64 #76140

Open

pedrobsaila added 2 commits August 31, 2024 23:13

fix build errors 3

0d2ba7b

fix build errors 4

3e8b530

build-analysis bot mentioned this pull request Aug 31, 2024

restarted. Azure DevOps can't recover from restarts. dotnet/dnceng#3879

Open

3 tasks

fix build errors 5

6ab5360

a74nh reviewed Sep 2, 2024

View reviewed changes

jakobbotsch reviewed Sep 2, 2024

View reviewed changes

JulieLeeMSFT assigned jakobbotsch Oct 7, 2024

JulieLeeMSFT added the needs-author-action An issue or pull request that requires more info or actions from the author. label Oct 7, 2024

dotnet-policy-service bot added the no-recent-activity label Oct 21, 2024

dotnet-policy-service bot closed this Nov 4, 2024

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Chained comparison of two integers against a constant is not coalesced #102103

Chained comparison of two integers against a constant is not coalesced #102103

pedrobsaila commented May 10, 2024

neon-sunset commented May 11, 2024

pedrobsaila commented May 12, 2024 •

edited

Loading

JulieLeeMSFT commented Jun 17, 2024

jakobbotsch commented Jul 1, 2024

azure-pipelines bot commented Jul 1, 2024

jakobbotsch Jul 1, 2024

jakobbotsch Jul 1, 2024

neon-sunset Jul 1, 2024 •

edited

Loading

pedrobsaila Jul 10, 2024 •

edited

Loading

jakobbotsch Jul 12, 2024

pedrobsaila commented Aug 28, 2024

a74nh Sep 2, 2024

a74nh commented Sep 2, 2024

jakobbotsch Sep 2, 2024

jakobbotsch Sep 2, 2024 •

edited

Loading

dotnet-policy-service bot commented Oct 21, 2024

dotnet-policy-service bot commented Nov 4, 2024

Chained comparison of two integers against a constant is not coalesced #102103

Chained comparison of two integers against a constant is not coalesced #102103

Conversation

pedrobsaila commented May 10, 2024

neon-sunset commented May 11, 2024

pedrobsaila commented May 12, 2024 • edited Loading

JulieLeeMSFT commented Jun 17, 2024

jakobbotsch commented Jul 1, 2024

azure-pipelines bot commented Jul 1, 2024

jakobbotsch Jul 1, 2024

Choose a reason for hiding this comment

jakobbotsch Jul 1, 2024

Choose a reason for hiding this comment

neon-sunset Jul 1, 2024 • edited Loading

Choose a reason for hiding this comment

pedrobsaila Jul 10, 2024 • edited Loading

Choose a reason for hiding this comment

jakobbotsch Jul 12, 2024

Choose a reason for hiding this comment

pedrobsaila commented Aug 28, 2024

a74nh Sep 2, 2024

Choose a reason for hiding this comment

a74nh commented Sep 2, 2024

jakobbotsch Sep 2, 2024

Choose a reason for hiding this comment

jakobbotsch Sep 2, 2024 • edited Loading

Choose a reason for hiding this comment

dotnet-policy-service bot commented Oct 21, 2024

dotnet-policy-service bot commented Nov 4, 2024

pedrobsaila commented May 12, 2024 •

edited

Loading

neon-sunset Jul 1, 2024 •

edited

Loading

pedrobsaila Jul 10, 2024 •

edited

Loading

jakobbotsch Sep 2, 2024 •

edited

Loading