Extract fgMorph(Init/Copy)Block into their own classes. #53983

sandreenko · 2021-06-10T07:51:47Z

The main goal of this change is to simplify fgMorph(Init/Copy)Block logic for future changes and current support.

I am not expecting anybody to read through all code movements so suggest you read through the changes outside of these functions and ready the new code to see if it is easy to follow and if something is unclear. This change is no-asm diff (a few preparation PRs were merged to achieve that).

The changes outside of the 2 target functions:

we now check that LHS of an assignment is marked as GTF_DONT_CSE and there were a few places where we were missing it, they were fixed.
IsLocalAddrExpr got a header and an additional argument, now for tree like ADD(LCL_VAR V01+16, 10) we would recover 10 as the offset, in the past were recording the sum fldSeq but not the offset.

sandreenko · 2021-06-10T07:53:01Z

/azp run runtime-coreclr jitstress

azure-pipelines · 2021-06-10T07:53:16Z

Azure Pipelines successfully started running 1 pipeline(s).

sandreenko · 2021-06-12T05:02:54Z

/azp run runtime-coreclr jitstress

azure-pipelines · 2021-06-12T05:03:10Z

Azure Pipelines successfully started running 1 pipeline(s).

sandreenko · 2021-06-13T07:09:05Z

/azp run runtime-coreclr jitstress, runtime-coreclr outerloop

azure-pipelines · 2021-06-13T07:09:36Z

Azure Pipelines successfully started running 2 pipeline(s).

sandreenko · 2021-06-23T08:33:50Z

/azp run runtime-coreclr jitstress, runtime-coreclr outerloop

azure-pipelines · 2021-06-23T08:34:19Z

Azure Pipelines successfully started running 2 pipeline(s).

sandreenko · 2021-06-24T08:58:59Z

src/coreclr/jit/morph.cpp

-                    // It would be nice if lvExactSize always corresponded to the size of the struct,
-                    // but it doesn't always for the temps that the importer creates when it spills side
-                    // effects.
-                    // TODO-Cleanup: Determine when this happens, and whether it can be changed.


The previous version was working wrong with StackAllocation enabled, for reference types getClassSize always returns TARGET_POINTER_SIZE that is not how many bytes it takes on the stack, to see how it was fixed search for compObjectStackAllocation()

sandreenko · 2021-06-24T09:01:22Z

src/coreclr/jit/morphblock.cpp

+                }
+                else
+                {
+                    assert(m_dstAddOff == 0);


there was a potential bug with trees like ADD(CNST X, ADD CNST Y, ADDR(LCL_VAR Z)) when we were morphing an assignment to field by field using the local var. In the past, we were ignoring X+Y offset for it. Lucky for us we don't have such cases.

sandreenko · 2021-06-24T09:02:13Z

src/coreclr/jit/morphblock.cpp

+
+    if (m_transformationDecision == BlockTransformation::Undefined)
+    {
+        GenTree* oneAsgTree = m_comp->fgMorphOneAsgBlockOp(m_asg);


I am planning to delete fgMorphOneAsgBlockOp later so it is why I did not bother to move it into this class.

sandreenko · 2021-06-24T09:07:21Z

src/coreclr/jit/morphblock.cpp

+
+        if (m_transformationDecision != BlockTransformation::FieldByField)
+        {
+            if (m_dst != m_dstLclNode)


this is an important change, in the past for ASG(struct<8> notPromotedStruct, 0) if we did not transform it as OneAsg (for example, the struct has holes and a custom layout) we would set lvaSetVarDoNotEnregister. Now we don't, LSRA won't try to enregister it because it can't enregister structs, but if we enable JitEnregStructLocals=1 we will start to see the diffs that we wanted. #52802 was an important step to make this pessimization deletion possible.

sandreenko · 2021-06-24T09:08:09Z

/azp run runtime-coreclr jitstress, runtime-coreclr outerloop

azure-pipelines · 2021-06-24T09:08:39Z

Azure Pipelines successfully started running 2 pipeline(s).

sandreenko · 2021-06-24T09:09:10Z

PTAL @BruceForstall, I think this is ready for review, cc @dotnet/jit-contrib

SingleAccretion · 2021-06-24T10:06:32Z

src/coreclr/jit/morphblock.cpp

+    if (m_result != m_asg)
+    {
+        m_result->gtDebugFlags |= GTF_DEBUG_NODE_MORPHED;
+    }


Nit: if you like terse debugging macros, this can be written as: DBEXEC(m_result != m_asg, m_result->gtDebugFlags |= GTF_DEBUG_NODE_MORPHED) (would allow to use JITDUMP & DISPTREE below).

Not a fan of it, will leave as if.

src/coreclr/jit/morphblock.cpp

SingleAccretion · 2021-06-24T10:26:49Z

src/coreclr/jit/morphblock.cpp

+    if (dynBlock->gtDynamicSize->IsCnsIntOrI())
+    {
+        GenTreeIntCon* dynSize = dynBlock->gtDynamicSize->AsIntCon();
+        assert(dynSize->FitsInI32());


Noting that this is an interesting assert in that it is actually testing that the constant node itself is well-formed. The implicit contract of CNS_INT of TYP_INT on 64 bit hosts is that the int32_t must be sign-extended to int64_t, which means that this assert will fail if something (say buggy GT_CAST folding...) creates dynSize with gtIconValue that is actually equal to UINT32_MAX (i. e. has upper bits set to zero), even as MorphDynamicBlock itself can work with such a constant (it won't be actually truncating anything).

SingleAccretion · 2021-06-24T10:34:25Z

src/coreclr/jit/morphblock.cpp

+        }
+        else if (m_dstDoFldAsg && dstFldIsProfitable)
+        {
+            // Match the following kinds of trees:


Just a note: would be nice to update these to the new dump format someday (which is much better in my opinion).

Thanks, I will change this method further and include it. For now, I need to do the biggest code movements, which we will merge mostly based on the fact that there are no diffs rather than checking each small code piece that was moved.
After that these methods would become available for more changes.

sandreenko · 2021-06-25T00:05:32Z

/azp run runtime-coreclr jitstress, runtime-coreclr outerloop

azure-pipelines · 2021-06-25T00:06:04Z

Azure Pipelines successfully started running 2 pipeline(s).

BruceForstall

LGTM. Looks like a nice cleanup, and framework for future work.

This is complicated enough that it seems like it would be useful to have a nice, long, file header comment describing the problem, what the code does, with some simple (and maybe even not so simple) examples. Like a design document/spec. That's not necessary for this change, but would be useful eventually to help people who need to work on the code in the future.

sandreenko added NO-REVIEW Experimental/testing PR, do NOT review it area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI labels Jun 10, 2021

sandreenko force-pushed the fgMorphCopyBlock branch from d8013f3 to d2f27c5 Compare June 13, 2021 05:19

sandreenko force-pushed the fgMorphCopyBlock branch 3 times, most recently from 75803b5 to b22c071 Compare June 23, 2021 07:29

sandreenko changed the title ~~test PR~~ Extract fgMorph(Init/Copy)Block into their own classes. Jun 23, 2021

sandreenko removed the NO-REVIEW Experimental/testing PR, do NOT review it label Jun 23, 2021

sandreenko force-pushed the fgMorphCopyBlock branch from b22c071 to 89d5d4d Compare June 24, 2021 08:54

sandreenko commented Jun 24, 2021

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sandreenko marked this pull request as ready for review June 24, 2021 09:08

SingleAccretion reviewed Jun 24, 2021

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SingleAccretion mentioned this pull request Jun 25, 2021

Fix bad folding #54722

Merged

runfoapp bot mentioned this pull request Jun 25, 2021

Test failure System.Threading.Tests.PeriodicTimerTests.WaitForNextTickAsync_CanceledWaitThenWaitAgain_Succeeds #54713

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BruceForstall approved these changes Jun 25, 2021

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Sergey added 3 commits June 25, 2021 16:09

Rewrite fgMorph(Copy/Init)Block.

496c7ef

fix a last squash error.

817d5ad

fix nits

94305c3

sandreenko force-pushed the fgMorphCopyBlock branch from 5b55600 to 94305c3 Compare June 25, 2021 23:11

sandreenko merged commit 6cccee5 into dotnet:main Jun 26, 2021

ghost locked as resolved and limited conversation to collaborators Jul 26, 2021

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Extract fgMorph(Init/Copy)Block into their own classes. #53983

Extract fgMorph(Init/Copy)Block into their own classes. #53983

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Extract fgMorph(Init/Copy)Block into their own classes. #53983

Extract fgMorph(Init/Copy)Block into their own classes. #53983

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