- Teach CanEvaluateInDifferentType of this xform: sext (zext ty1), ty2 -> zext ty2

- Looking at the number of sign bits of the a sext instruction to determine  whether new trunc + sext pair should be added when its source is being evaluated in a different type.

llvm-svn: 62263

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/cast-sext-zext.ll b/llvm/test/Transforms/InstCombine/cast-sext-zext.ll
new file mode 100644
index 00000000000..da5e7facfad
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/cast-sext-zext.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep sext
+
+define zeroext i16 @t(i8 zeroext %on_off, i16* nocapture %puls) nounwind readonly {
+entry:
+	%0 = zext i8 %on_off to i32
+	%1 = add i32 %0, -1
+	%2 = sext i32 %1 to i64
+	%3 = getelementptr i16* %puls, i64 %2
+	%4 = load i16* %3, align 2
+	ret i16 %4
+}