[AMDGPU] Rematerialize VGPR candidates when SGPR spills results in VGPR Excess (#168079)

Before, when selecting candidates to rematerialize, we would only
consider SGPR candidates when there was an excess of SGPR registers.

Failing to eliminate the excess would result in spills to VGPRs.
This is normally not an issue, unless spilling to VGPRs results in
excess VGPRs.

This patch does 2 things:
* It relaxes the GCNRPTarget success criteria: now we accept regions
  where we spill SGPRs to VGPRs, as long as this does not end up in
  excess VGPRs.
* It changes isSaveBeneficial to consider the excess VGPRs (which
  includes the SGPRs that would be spilled to VGPR).

With these changes, the compiler rematerializes VGPRs when the excess
SGPRs would result in VGPR excess.

This has some unaddressed flaws: we should attempt to rematerialize
SGPRs
first in order to eliminate the SGPR excess that results in VGPR excess.

Related to SWDEV-549940
4 files changed
tree: 91a35d1b2e4dec4dd66b2409a8c5a4c56f4c510b
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libsycl/
  16. libunwind/
  17. lld/
  18. lldb/
  19. llvm/
  20. llvm-libgcc/
  21. mlir/
  22. offload/
  23. openmp/
  24. orc-rt/
  25. polly/
  26. runtimes/
  27. third-party/
  28. utils/
  29. .clang-format
  30. .clang-format-ignore
  31. .clang-tidy
  32. .git-blame-ignore-revs
  33. .gitattributes
  34. .gitignore
  35. .mailmap
  36. CODE_OF_CONDUCT.md
  37. CONTRIBUTING.md
  38. LICENSE.TXT
  39. pyproject.toml
  40. README.md
  41. SECURITY.md
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