Fix mishandling of the infinite loop case when merging two blocks. This

fixes PR2540.

llvm-svn: 53533

1 files changed, 36 insertions, 0 deletions

diff --git a/llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll b/llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
new file mode 100644
index 00000000000..0678e20ed4a
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/2008-07-13-InfLoopMiscompile.ll
@@ -0,0 +1,36 @@
+; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | grep {%outval = phi i32 .*mux}
+; PR2540
+; Outval should end up with a select from 0/2, not all constants.
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
+target triple = "i386-pc-linux-gnu"
+@g_37 = common global i32 0		; <i32*> [#uses=1]
+@.str = internal constant [4 x i8] c"%d\0A\00"		; <[4 x i8]*> [#uses=1]
+
+define i32 @main() nounwind  {
+entry:
+	%l = load i32* @g_37, align 4		; <i32> [#uses=1]
+	%cmpa = icmp ne i32 %l, 0		; <i1> [#uses=3]
+	br i1 %cmpa, label %func_1.exit, label %mooseblock
+
+mooseblock:		; preds = %entry
+	%cmpb = icmp eq i1 %cmpa, false		; <i1> [#uses=2]
+	br i1 %cmpb, label %monkeyblock, label %beeblock
+
+monkeyblock:		; preds = %monkeyblock, %mooseblock
+	br i1 %cmpb, label %cowblock, label %monkeyblock
+
+beeblock:		; preds = %beeblock, %mooseblock
+	br i1 %cmpa, label %cowblock, label %beeblock
+
+cowblock:		; preds = %beeblock, %monkeyblock
+	%cowval = phi i32 [ 2, %beeblock ], [ 0, %monkeyblock ]		; <i32> [#uses=1]
+	br label %func_1.exit
+
+func_1.exit:		; preds = %cowblock, %entry
+	%outval = phi i32 [ %cowval, %cowblock ], [ 1, %entry ]		; <i32> [#uses=1]
+	%pout = tail call i32 (i8*, ...)* @printf( i8* noalias  getelementptr ([4 x i8]* @.str, i32 0, i32 0), i32 %outval ) nounwind 		; <i32> [#uses=0]
+	ret i32 0
+}
+
+declare i32 @printf(i8*, ...) nounwind