Improving quantized matmul performance by devectorizing shader.

[trivedivivek]

Summary:
This diff improves the performance of quantized matrix multiplication by devectorizing the shader.

An example modification is shown below:

// Before
VEC4_T sums[TILE_ROWS][TILE_TXCOLS];

// After
T sums[TILE_ROWS * TILE_TXCOLS * 4];

// Before
sums[r][${c}] = VEC4_T(0.0);

// After
for (int j = 0; j < 4; j++) {
    sums[r * TILE_TXCOLS * 4 + ${c} * 4 + j] = T(0.0);
}

Differential Revision: D85023829

[pytorch-bot]

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• AWS was down, GHA infrastructure effected / recovering

❌ 8 New Failures, 2 Unrelated Failures

As of commit b831b18 with merge base 0a1dfb2 ():

NEW FAILURES - The following jobs have failed:

• pull / android / run-emulator (gh)
  The process '/usr/bin/sh' failed with exit code 255
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t e0fef530deba5e97665fc7560aa2baf95b6d3828c3c5be2cc4fbcc554112b2f8 /exec failed with exit code 1
• pull / unittest-arm-backend-with-no-fvp (test_pytest_models) / linux-job (gh)
  RuntimeError: Command docker exec -t 0e2ce92b2f3c3a34e23c9ab9f08494679a6406623912142ff7b95ccb7471223b /exec failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t a60486e2b38613961fcc5b8f0830a800995c06ea1fddea5a33a7ddf5968c9ca3 /exec failed with exit code 1
• Test CUDA Builds / export-voxtral-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t f49de6da0b0be081ee1730670e545fc6d4b2701971069ba84259a493c34bb876 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t 71e42c2235aad24e10721467e3ab760960cb8e965b1db02b8ae5a0979cdeccc1 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-weight-only / linux-job (gh)
  RuntimeError: Command docker exec -t 506a0f48cbb18fe759d3c6b3daa111055cbe4bd6af2b6e15721d87b3cf0c8dab /exec failed with exit code 2
• Test Metal Backend / export-voxtral-metal-artifact / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 2

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / unittest / linux / linux-job (gh) (matched linux rule in flaky-rules.json)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.

BROKEN TRUNK - The following job failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest-editable / linux / linux-job (gh) (trunk failure)

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[meta-codesync]

@trivedivivek has exported this pull request. If you are a Meta employee, you can view the originating Diff in D85023829.