[PATCH] D66334: [LoopUnroll] Handle certain PHIs in full unrolling properly.

[Bevin Hansson via Phabricator via llvm-commits]

ebevhan updated this revision to Diff 215561.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D66334/new/

https://reviews.llvm.org/D66334

Files:
  lib/Transforms/Utils/LoopUnroll.cpp
  test/Transforms/LoopUnroll/full-unroll-miscompile.ll


Index: test/Transforms/LoopUnroll/full-unroll-miscompile.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopUnroll/full-unroll-miscompile.ll
@@ -0,0 +1,68 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S -loop-unroll | FileCheck %s
+
+; The phi which acts as input to func should not be undef. It should
+; have its loop-carried value (the load of d in the entry block)
+; replaced accordingly after unrolling the loop.
+
+ at a = dso_local global i16 0, align 1
+ at b = dso_local global i16 0, align 1
+ at c = dso_local global [2 x i16] [i16 1, i16 1], align 1
+ at d = dso_local global i16 0, align 1
+ at e = dso_local global i64 0, align 1
+
+; Function Attrs: minsize nounwind optsize
+define dso_local i16 @main() #0 {
+; CHECK-LABEL: @main(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP:%.*]] = load i16, i16* @a, align 1
+; CHECK-NEXT:    [[TMP1:%.*]] = load i16, i16* getelementptr inbounds ([2 x i16], [2 x i16]* @c, i32 0, i32 0), align 1
+; CHECK-NEXT:    [[DIV:%.*]] = sdiv i16 [[TMP]], [[TMP1]]
+; CHECK-NEXT:    store i16 [[DIV]], i16* @b, align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = load i16, i16* @d, align 1
+; CHECK-NEXT:    br label [[FOR_COND:%.*]]
+; CHECK:       for.cond:
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP3:%.*]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    [[DOTLCSSA10_LCSSA:%.*]] = phi i16 [ [[TMP2]], [[FOR_COND_CLEANUP3]] ]
+; CHECK-NEXT:    store i16 [[DOTLCSSA10_LCSSA]], i16* @b, align 1
+; CHECK-NEXT:    store i64 1, i64* @e, align 1
+; CHECK-NEXT:    [[TMP3:%.*]] = call i16 @func(i16 [[DOTLCSSA10_LCSSA]])
+; CHECK-NEXT:    ret i16 0
+; CHECK:       for.cond.cleanup3:
+; CHECK-NEXT:    br i1 false, label [[FOR_COND_CLEANUP3_1:%.*]], label [[FOR_COND_CLEANUP:%.*]]
+; CHECK:       for.cond.cleanup3.1:
+; CHECK-NEXT:    unreachable
+;
+entry:
+  %tmp = load i16, i16* @a, align 1
+  %tmp1 = load i16, i16* getelementptr inbounds ([2 x i16], [2 x i16]* @c, i32 0, i32 0), align 1
+  %div = sdiv i16 %tmp, %tmp1
+  store i16 %div, i16* @b, align 1
+  %tmp2 = load i16, i16* @d, align 1
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.cond.cleanup3, %entry
+  %.lcssa10 = phi i16 [ %div, %entry ], [ %.lcssa, %for.cond.cleanup3 ]
+  %i.0 = phi i64 [ 37, %entry ], [ %inc9, %for.cond.cleanup3 ]
+  %cmp = icmp ult i64 %i.0, 38
+  br i1 %cmp, label %for.cond.cleanup3, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond
+  %.lcssa10.lcssa = phi i16 [ %.lcssa10, %for.cond ]
+  store i16 %.lcssa10.lcssa, i16* @b, align 1
+  store i64 1, i64* @e, align 1
+  %tmp3 = call i16 (i16) @func(i16 %.lcssa10.lcssa)
+  ret i16 0
+
+for.cond.cleanup3:                                ; preds = %for.cond
+  %.lcssa = phi i16 [ %tmp2, %for.cond ]
+  %inc9 = add i64 %i.0, 1
+  br label %for.cond
+}
+
+; Function Attrs: nounwind
+declare i16 @func(i16) #1
+
+attributes #0 = { minsize nounwind optsize }
+attributes #1 = { nounwind }
Index: lib/Transforms/Utils/LoopUnroll.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnroll.cpp
+++ lib/Transforms/Utils/LoopUnroll.cpp
@@ -723,7 +723,7 @@
       if (Dest != LoopExit) {
         BasicBlock *BB = Src;
         for (BasicBlock *Succ : successors(BB)) {
-          if (Succ == CurrentHeader)
+          if (Succ == CurrentHeader || Succ == Dest)
             continue;
           for (PHINode &Phi : Succ->phis())
             Phi.removeIncomingValue(BB, false);


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