[PATCH] D64368: [LoopUnroll] do not unroll loops containing callbr

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers updated this revision to Diff 208513.
nickdesaulniers added a comment.

- add back previous fixes from v2


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64368/new/

https://reviews.llvm.org/D64368

Files:
  llvm/lib/Analysis/LoopInfo.cpp
  llvm/test/Transforms/LoopUnroll/callbr.ll


Index: llvm/test/Transforms/LoopUnroll/callbr.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopUnroll/callbr.ll
@@ -0,0 +1,51 @@
+; RUN: opt -loop-unroll -S -o - %s | FileCheck %s
+
+; Check that the loop body exists.
+; CHECK: for.body
+; CHECK: if.then
+; CHECK: asm.fallthrough
+; CHECK: l_yes
+; CHECK: for.inc
+
+; Check that the loop body does not get unrolled.  We could modify this test in
+; the future to support loop unrolling callbr's IFF we checked that the callbr
+; operands were unrolled/updated correctly, as today they are not.
+; CHECK-NOT: if.then.1
+; CHECK-NOT: asm.fallthrough.1
+; CHECK-NOT: l_yes.1
+; CHECK-NOT: for.inc.1
+; CHECK-NOT: if.then.2
+; CHECK-NOT: asm.fallthrough.2
+; CHECK-NOT: l_yes.2
+; CHECK-NOT: for.inc.2
+
+define dso_local void @d() {
+entry:
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.inc
+  ret void
+
+for.body:                                         ; preds = %for.inc, %entry
+  %e.04 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+  %tobool = icmp eq i32 %e.04, 0
+  br i1 %tobool, label %for.inc, label %if.then
+
+if.then:                                          ; preds = %for.body
+  callbr void asm sideeffect "1: nop\0A\09.quad b, ${0:l}, $$5\0A\09", "X,~{dirflag},~{fpsr},~{flags}"(i8* blockaddress(@d, %l_yes))
+          to label %asm.fallthrough [label %l_yes]
+
+asm.fallthrough:                                  ; preds = %if.then
+  br label %l_yes
+
+l_yes:                                            ; preds = %asm.fallthrough, %if.then
+  %call = tail call i32 (...) @g()
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %l_yes
+  %inc = add nuw nsw i32 %e.04, 1
+  %exitcond = icmp eq i32 %inc, 3
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+}
+
+declare dso_local i32 @g(...) local_unnamed_addr
Index: llvm/lib/Analysis/LoopInfo.cpp
===================================================================
--- llvm/lib/Analysis/LoopInfo.cpp
+++ llvm/lib/Analysis/LoopInfo.cpp
@@ -432,8 +432,11 @@
 bool Loop::isSafeToClone() const {
   // Return false if any loop blocks contain indirectbrs, or there are any calls
   // to noduplicate functions.
+  // FIXME: it should be ok to clone CallBrInst's if we correctly update the
+  // operand list to reflect the newly cloned labels.
   for (BasicBlock *BB : this->blocks()) {
-    if (isa<IndirectBrInst>(BB->getTerminator()))
+    if (isa<IndirectBrInst>(BB->getTerminator()) ||
+        isa<CallBrInst>(BB->getTerminator()))
       return false;
 
     for (Instruction &I : *BB)


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