[llvm] [LV] Support tail-folded epilogue loops (PR #208764)

[David Sherwood via llvm-commits]

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@@ -120,26 +152,31 @@ for.end:
   ret i32 0
 }
 
-define i1 @early_exit(ptr %A, i64 %n, i8 %find) {
+define i64 @early_exit(ptr dereferenceable(1024) align 8 %src, i1 %cond) {
 ; CHECK-DISABLED-EARLY-EXIT-LABEL: LV: Checking a loop in 'early_exit'
 ; CHECK-DISABLED-EARLY-EXIT: remark: <unknown>:0:0: Epilogue tail-folding is not supported yet for early-exit loops
 ;
 entry:
-  br label %for.body
+  br label %loop.header
 
-for.body:
-  %iv = phi i64 [ 0, %entry ], [ %iv.next, %cont ]
-  %arrayidx = getelementptr inbounds i8, ptr %A, i64 %iv
-  %val = load i8, ptr %arrayidx, align 1
-  %exitcond = icmp eq i8 %val, %find
-  br i1 %exitcond, label %exit, label %cont
+loop.header:
+  %iv = phi i64 [ %iv.next, %latch ], [ 0, %entry ]
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david-arm wrote:

I think some of these changes (and the new test perhaps?) can be committed separately in a NFC patch to reduce the diff. For example, the changes to `@test_outer_loop` and `@early_exit`.

https://github.com/llvm/llvm-project/pull/208764