[llvm] [Uniformity] Fixed control-div early stop (PR #139667)

[Junjie Gu via llvm-commits]

jgu222 wrote:

@ssahasra  Given the following:
` 
; RUN: opt %s -mtriple amdgcn-- -passes='print<uniformity>' -disable-output 2>&1 | FileCheck %s

define amdgpu_kernel void @cycle_inner_ipd(i32 %n, i32 %a, i32 %b) #0 {
;
;          entry(6)
;        /      \
;     E2(5)<----E1(1)
;       | \     ^^
;       |  \  /  |
;       |   A(4) |
;       |  /     |
;       | /      |
;     B(3) ----->C(2)
;                |
;                X(0)
;
;
;
entry:
  %tid = call i32 @llvm.amdgcn.workitem.id.x()
  %div.cond = icmp slt i32 %tid, 0
  %uni.cond = icmp slt i32 %a, 0
  %uni.cond1 = icmp slt i32 %a, 2
  %uni.cond2 = icmp slt i32 %a, 10
  br i1 %uni.cond, label %E2, label %E1

E1:
  br label %E2

E2:
  br i1 %uni.cond1, label %A, label %B


A:
  br i1 %div.cond, label %E1, label %B

B:
  %div.merge = phi i32 [ 0, %A ], [ %b, %E2 ]
  br label %C

C:
  br i1 %uni.cond2, label %E1, label %X

X:
  ret void
}
'

https://github.com/llvm/llvm-project/pull/139667