Implement PR1777 by detecting dependent phis that

all compute the same value.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43777 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 31 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/phi-merge.ll b/test/Transforms/InstCombine/phi-merge.ll
new file mode 100644
index 0000000..daac412
--- /dev/null
+++ b/test/Transforms/InstCombine/phi-merge.ll
@@ -0,0 +1,31 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep {phi i32}
+; PR1777
+
+declare i1 @rrr()
+
+define i1 @zxcv() {
+entry:
+%a = alloca i32
+%i = ptrtoint i32* %a to i32
+%b = call i1 @rrr()
+br i1 %b, label %one, label %two
+
+one:
+%x = phi i32 [%i, %entry], [%y, %two]
+%c = call i1 @rrr()
+br i1 %c, label %two, label %end
+
+two:
+%y = phi i32 [%i, %entry], [%x, %one]
+%d = call i1 @rrr()
+br i1 %d, label %one, label %end
+
+end:
+%f = phi i32 [ %x, %one], [%y, %two]
+; Change the %f to %i, and the optimizer suddenly becomes a lot smarter
+; even though %f must equal %i at this point
+%g = inttoptr i32 %f to i32*
+store i32 10, i32* %g
+%z = call i1 @rrr()
+ret i1 %z
+}