When rewriting the loop exit test with the canonical induction variable,

leave the original comparison in place if it has other uses, since the
other uses won't be dominated by the new comparison instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72369 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index f20d424724ab275d106233570a1c46a4cc3e5bed..07c7d0071fb6b95df9a9bd06507aad6b8c4b6aaf 100644 (file)
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -187,7 +187,12 @@ ICmpInst *IndVarSimplify::LinearFunctionTestReplace(Loop *L,
   ICmpInst *Cond = new ICmpInst(Opcode, CmpIndVar, ExitCnt, "exitcond", BI);
 
   Instruction *OrigCond = cast<Instruction>(BI->getCondition());
-  OrigCond->replaceAllUsesWith(Cond);
+  // It's tempting to use replaceAllUsesWith here to fully replace the old
+  // comparison, but that's not immediately safe, since users of the old
+  // comparison may not be dominated by the new comparison. Instead, just
+  // update the branch to use the new comparison; in the common case this
+  // will make old comparison dead.
+  BI->setCondition(Cond);
   RecursivelyDeleteTriviallyDeadInstructions(OrigCond);
 
   ++NumLFTR;

diff --git a/test/Transforms/IndVarSimplify/lftr-other-uses.ll b/test/Transforms/IndVarSimplify/lftr-other-uses.ll
new file mode 100644 (file)
index 0000000..c8f1e95
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/lftr-other-uses.ll
@@ -0,0 +1,36 @@
+; RUN: llvm-as < %s | opt -indvars -disable-output
+
+; Don't RAUW the loop's original comparison instruction if it has
+; other uses which aren't dominated by the new comparison instruction.
+
+       %struct.DecRefPicMarking_s = type { i32, i32, i32, i32, i32, %struct.DecRefPicMarking_s* }
+       %struct.datapartition = type { %typedef.Bitstream*, %typedef.DecodingEnvironment, i32 (%struct.syntaxelement*, %struct.img_par*, %struct.inp_par*, %struct.datapartition*)* }
+       %struct.img_par = type { i32, i32, i32, i32, i32*, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, [16 x [16 x i16]], [6 x [32 x i32]], [16 x [16 x i32]], [4 x [12 x [4 x [4 x i32]]]], [16 x i32], i32**, i32*, i32***, i32**, i32, i32, i32, i32, %typedef.Slice*, %struct.macroblock*, i32, i32, i32, i32, i32, i32, i32**, %struct.DecRefPicMarking_s*, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, [3 x i32], i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32***, i32***, i32****, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, %struct.timeb, %struct.timeb, i32, i32, i32, i32, i32, i32, i32, i32 }
+       %struct.inp_par = type { [100 x i8], [100 x i8], [100 x i8], i32, i32, i32, i32, i32, i32, i32 }
+       %struct.macroblock = type { i32, i32, i32, %struct.macroblock*, %struct.macroblock*, i32, [2 x [4 x [4 x [2 x i32]]]], i32, i64, i64, i32, i32, [4 x i32], [4 x i32], i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 }
+       %struct.syntaxelement = type { i32, i32, i32, i32, i32, i32, i32, i32, void (i32, i32, i32*, i32*)*, void (%struct.syntaxelement*, %struct.inp_par*, %struct.img_par*, %typedef.DecodingEnvironment*)* }
+       %struct.timeb = type { i32, i16, i16, i16 }
+       %typedef.BiContextType = type { i16, i8 }
+       %typedef.Bitstream = type { i32, i32, i32, i32, i8*, i32 }
+       %typedef.DecodingEnvironment = type { i32, i32, i32, i32, i32, i8*, i32* }
+       %typedef.MotionInfoContexts = type { [4 x [11 x %typedef.BiContextType]], [2 x [9 x %typedef.BiContextType]], [2 x [10 x %typedef.BiContextType]], [2 x [6 x %typedef.BiContextType]], [4 x %typedef.BiContextType], [4 x %typedef.BiContextType], [3 x %typedef.BiContextType] }
+       %typedef.Slice = type { i32, i32, i32, i32, i32, i32, i32, i32, i32, %struct.datapartition*, %typedef.MotionInfoContexts*, %typedef.TextureInfoContexts*, i32, i32*, i32*, i32*, i32, i32*, i32*, i32*, i32 (%struct.img_par*, %struct.inp_par*)*, i32, i32, i32, i32 }
+       %typedef.TextureInfoContexts = type { [2 x %typedef.BiContextType], [4 x %typedef.BiContextType], [3 x [4 x %typedef.BiContextType]], [10 x [4 x %typedef.BiContextType]], [10 x [15 x %typedef.BiContextType]], [10 x [15 x %typedef.BiContextType]], [10 x [5 x %typedef.BiContextType]], [10 x [5 x %typedef.BiContextType]], [10 x [15 x %typedef.BiContextType]], [10 x [15 x %typedef.BiContextType]] }
+
+define void @readCBP_CABAC(%struct.syntaxelement* %se, %struct.inp_par* %inp, %struct.img_par* %img.1, %typedef.DecodingEnvironment* %dep_dp) {
+entry:
+       br label %loopentry.0
+
+loopentry.0:           ; preds = %loopentry.1, %entry
+       %mb_y.0 = phi i32 [ 0, %entry ], [ %tmp.152, %loopentry.1 ]             ; <i32> [#uses=2]
+       %tmp.14 = icmp sle i32 %mb_y.0, 3               ; <i1> [#uses=2]
+       %tmp.15 = zext i1 %tmp.14 to i32                ; <i32> [#uses=0]
+       br i1 %tmp.14, label %loopentry.1, label %loopexit.0
+
+loopentry.1:           ; preds = %loopentry.0
+       %tmp.152 = add i32 %mb_y.0, 2           ; <i32> [#uses=1]
+       br label %loopentry.0
+
+loopexit.0:            ; preds = %loopentry.0
+       unreachable
+}