JIT: Add FlowEdge destination block member

[amanasifkhalid]

Part of #93020. Per conversation in #98054, I'm going to try to replace BasicBlock's block successor pointers (bbTarget, bbFalseTarget, etc) with FlowEdge pointers to simplify access to successor edges. To do this, each edge is going to need access to its destination block, so that access to successor blocks is still simple. As a first step, add a destination block member to FlowEdge.

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Part of #93020. Per conversation in #98054, I'm going to try to replace BasicBlock's block successor pointers (bbTarget, bbFalseTarget, etc) with FlowEdge pointers to simplify access to successor edges. To do this, each edge is going to need access to its destination block, so that access to successor blocks is still simple. As a first step, add a destination block member to FlowEdge.

Author:	amanasifkhalid
Assignees:	amanasifkhalid
Labels:	area-CodeGen-coreclr
Milestone:	-

[ryujit-bot]

Diff results for #98243

Throughput diffs

Throughput diffs for windows/arm64 ran on windows/x64

MinOpts (-0.00% to +0.01%)

Collection	PDIFF
libraries.pmi.windows.arm64.checked.mch	+0.01%
realworld.run.windows.arm64.checked.mch	+0.01%

Details here

---

Throughput diffs for linux/arm ran on windows/x86

Overall (+0.00% to +0.01%)

Collection	PDIFF
benchmarks.run.linux.arm.checked.mch	+0.01%
benchmarks.run_pgo.linux.arm.checked.mch	+0.01%
benchmarks.run_tiered.linux.arm.checked.mch	+0.01%
libraries.crossgen2.linux.arm.checked.mch	+0.01%
libraries.pmi.linux.arm.checked.mch	+0.01%
libraries_tests.run.linux.arm.Release.mch	+0.01%
libraries_tests_no_tiered_compilation.run.linux.arm.Release.mch	+0.01%
realworld.run.linux.arm.checked.mch	+0.01%

FullOpts (+0.01%)

Collection	PDIFF
benchmarks.run.linux.arm.checked.mch	+0.01%
benchmarks.run_pgo.linux.arm.checked.mch	+0.01%
benchmarks.run_tiered.linux.arm.checked.mch	+0.01%
coreclr_tests.run.linux.arm.checked.mch	+0.01%
libraries.crossgen2.linux.arm.checked.mch	+0.01%
libraries.pmi.linux.arm.checked.mch	+0.01%
libraries_tests.run.linux.arm.Release.mch	+0.01%
libraries_tests_no_tiered_compilation.run.linux.arm.Release.mch	+0.01%
realworld.run.linux.arm.checked.mch	+0.01%

Throughput diffs for windows/x86 ran on windows/x86

Overall (+0.00% to +0.01%)

Collection	PDIFF
benchmarks.run.windows.x86.checked.mch	+0.01%
benchmarks.run_pgo.windows.x86.checked.mch	+0.01%
libraries_tests.run.windows.x86.Release.mch	+0.01%
libraries_tests_no_tiered_compilation.run.windows.x86.Release.mch	+0.01%

FullOpts (+0.00% to +0.01%)

Collection	PDIFF
benchmarks.run.windows.x86.checked.mch	+0.01%
benchmarks.run_pgo.windows.x86.checked.mch	+0.01%
benchmarks.run_tiered.windows.x86.checked.mch	+0.01%
libraries_tests.run.windows.x86.Release.mch	+0.01%
libraries_tests_no_tiered_compilation.run.windows.x86.Release.mch	+0.01%

Details here

---

[amanasifkhalid]

cc @dotnet/jit-contrib, @AndyAyersMS PTAL. This is a somewhat vain attempt to split up the successor edge work into smaller changes. I anticipate the next PR -- replacing the successor block pointers with successor edge pointers in BasicBlock -- will be quite large.

[AndyAyersMS]

Note we will get the memory back (and then some) when we remove the min and max edge weights.