[PATCH] D157495: [WIP] Run SimplifyCFG from Atomic-Expand on CAS loop blocks.

[Pravin Jagtap via Phabricator via llvm-commits]

pravinjagtap added inline comments.


================
Comment at: llvm/test/Transforms/AtomicExpand/AMDGPU/expand-atomic-simplify-cfg-CAS-block.ll:24
+; GFX90A-NEXT:    [[TMP4]] = bitcast i32 [[NEWLOADED]] to float
+; GFX90A-NEXT:    br i1 [[SUCCESS]], label [[ENDIF:%.*]], label [[ATOMICRMW_START]]
+; GFX90A:       else:
----------------
pravinjagtap wrote:
> Here, we can observe the potential benefits of running simplify CFG. It simplifies the branching. 
Without this it would have been:

``` 
; GFX90A:       atomicrmw.start:	
; GFX90A-NEXT:    [[LOADED:%.*]] = phi float [ [[TMP0]], [[IF]] ], [ [[TMP4:%.*]], [[ATOMICRMW_START]] ]	
; GFX90A-NEXT:    [[NEW:%.*]] = fadd float [[LOADED]], [[IN:%.*]]	
; GFX90A-NEXT:    [[TMP1:%.*]] = bitcast float [[NEW]] to i32	
; GFX90A-NEXT:    [[TMP2:%.*]] = bitcast float [[LOADED]] to i32	
; GFX90A-NEXT:    [[TMP3:%.*]] = cmpxchg ptr addrspace(1) [[OUT]], i32 [[TMP2]], i32 [[TMP1]] seq_cst seq_cst, align 4	
; GFX90A-NEXT:    [[SUCCESS:%.*]] = extractvalue { i32, i1 } [[TMP3]], 1	
; GFX90A-NEXT:    [[NEWLOADED:%.*]] = extractvalue { i32, i1 } [[TMP3]], 0	
; GFX90A-NEXT:    [[TMP4]] = bitcast i32 [[NEWLOADED]] to float	
; GFX90A-NEXT:    br i1 [[SUCCESS]], label [[ATOMICRMW_END:%.*]], label [[ATOMICRMW_START]]	
; GFX90A:       atomicrmw.end:	
; GFX90A-NEXT:    br label [[ENDIF:%.*]]	
; GFX90A:       else:	
; GFX90A-NEXT:    [[TMP5:%.*]] = load float, ptr addrspace(1) [[OUT]], align 4	
; GFX90A-NEXT:    br label [[ATOMICRMW_START2:%.*]]	
; GFX90A:       atomicrmw.start2:	

````


Repository:
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  https://reviews.llvm.org/D157495/new/

https://reviews.llvm.org/D157495