[llvm] [AMDGPU] Set total VGPRs to 1536 for gfx12 (PR #96272)

[Shilei Tian via llvm-commits]

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@@ -1572,7 +1572,8 @@ def FeatureISAVersion12 : FeatureSet<
    FeatureVGPRSingleUseHintInsts,
    FeatureScalarDwordx3Loads,
    FeatureDPPSrc1SGPR,
-   FeatureMaxHardClauseLength32]>;
+   FeatureMaxHardClauseLength32,
+   Feature1_5xVGPRs]>;
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shiltian wrote:

Is it true for all GFX12? The SGP seems to say something else.

https://github.com/llvm/llvm-project/pull/96272