Don't assume it's safe to transform a loop just because it's dominated by any

comparison. Fixes bug 1598.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40866 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 0039144d897fbb92a1953fa7244905e5c905a47d..879347f7f72a4be21a9d0dbacbc311fb7c901a1b 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2387,7 +2387,7 @@ HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L) {
             return UnknownValue;  // Not a comparison against 'n-1'.
         }
         else return UnknownValue;
-      } else if (Cond == ICmpInst::ICMP_ULT)
+      } else
         return UnknownValue;
 
       // cerr << "Computed Loop Trip Count as: " 

diff --git a/test/Analysis/ScalarEvolution/2007-09-06-MisinterpretBranch.ll b/test/Analysis/ScalarEvolution/2007-09-06-MisinterpretBranch.ll
new file mode 100644 (file)
index 0000000..e3393d5
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/2007-09-06-MisinterpretBranch.ll
@@ -0,0 +1,18 @@
+; RUN: llvm-as < %s | opt -indvars -adce -simplifycfg | llvm-dis | grep "icmp s"
+; PR1598
+
+define i32 @f(i32 %a, i32 %b, i32 %x, i32 %y) {
+entry:
+       %tmp3 = icmp eq i32 %a, %b              ; <i1> [#uses=1]
+       br i1 %tmp3, label %return, label %bb
+
+bb:            ; preds = %bb, %entry
+       %x_addr.0 = phi i32 [ %tmp6, %bb ], [ %x, %entry ]              ; <i32> [#uses=1]
+       %tmp6 = add i32 %x_addr.0, 1            ; <i32> [#uses=3]
+       %tmp9 = icmp slt i32 %tmp6, %y          ; <i1> [#uses=1]
+       br i1 %tmp9, label %bb, label %return
+
+return:                ; preds = %bb, %entry
+       %x_addr.1 = phi i32 [ %x, %entry ], [ %tmp6, %bb ]              ; <i32> [#uses=1]
+       ret i32 %x_addr.1
+}