[PATCH] D81140: [Peeling] Extend the scope of peeling a bit

[Serguei Katkov via Phabricator via llvm-commits]

skatkov created this revision.
skatkov added reviewers: reames, ashlykov, fhahn.
Herald added subscribers: dantrushin, zzheng, hiraditya.
Herald added a project: LLVM.

Currently we allow peeling of the loops if there is a exiting latch block
and all other exits are blocks ending with deopt.

Actually we want that exit would end up with deopt unconditionally but
it is not required that exit itself ends with deopt.


https://reviews.llvm.org/D81140

Files:
  llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
  llvm/lib/Transforms/Utils/LoopUtils.cpp
  llvm/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-pd.ll


Index: llvm/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-pd.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-pd.ll
@@ -0,0 +1,47 @@
+; RUN: opt < %s -S -loop-unroll -unroll-runtime -unroll-peel-multi-deopt-exit 2>&1 | FileCheck %s
+
+; Make sure that we can peel even if deopt block is not in immidiate exit.
+
+; CHECK-LABEL: @basic
+; CHECK: br i1 %c, label %{{.*}}, label %side_exit
+; CHECK: br i1 %{{.*}}, label %[[NEXT0:.*]], label %exit
+; CHECK: [[NEXT0]]:
+; CHECK: br i1 %c, label %{{.*}}, label %side_exit
+; CHECK: br i1 %{{.*}}, label %[[NEXT1:.*]], label %exit
+
+define i32 @basic(i32* %p, i32 %k, i1 %c) #0 !prof !1 {
+entry:
+  %cmp3 = icmp slt i32 0, %k
+  br i1 %cmp3, label %header, label %deopt
+
+header:
+  br label %body
+
+body:
+  %i = phi i32 [ 0, %header ], [ %inc, %backedge ]
+  %addr = getelementptr inbounds i32, i32* %p, i32 %i
+  store i32 %i, i32* %addr, align 4
+  %inc = add nsw i32 %i, 1
+  %cmp = icmp slt i32 %inc, %k
+  br i1 %c, label %backedge, label %side_exit, !prof !3
+
+backedge:
+  br i1 %cmp, label %body, label %exit, !prof !2
+
+exit:
+  ret i32 %i
+
+side_exit:
+  br label %deopt
+
+deopt:
+  %deopt_kind = phi i32 [0, %entry], [1, %side_exit]
+  %rval = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 %deopt_kind) ]
+  ret i32 %rval
+}
+
+declare i32 @llvm.experimental.deoptimize.i32(...)
+
+!1 = !{!"function_entry_count", i64 1}
+!2 = !{!"branch_weights", i32 0, i32 1}
+!3 = !{!"branch_weights", i32 1, i32 0}
Index: llvm/lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -744,7 +744,7 @@
   SmallVector<BasicBlock *, 4> ExitBlocks;
   L->getUniqueNonLatchExitBlocks(ExitBlocks);
   if (any_of(ExitBlocks, [](const BasicBlock *EB) {
-        return !EB->getTerminatingDeoptimizeCall();
+        return !EB->getPostdominatingDeoptimizeCall();
       }))
     return nullptr;
 
Index: llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -90,7 +90,7 @@
       const BranchInst *T = dyn_cast<BranchInst>(Latch->getTerminator());
       return T && T->isConditional() && L->isLoopExiting(Latch) &&
              all_of(Exits, [](const BasicBlock *BB) {
-               return BB->getTerminatingDeoptimizeCall();
+               return BB->getPostdominatingDeoptimizeCall();
              });
     }
   }


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