The DAGCombiner was threading select over pairs of extending loads even

if the extension types were not the same.  The result was that if you
fed a select with sext and zext loads, as in the testcase, then it
would get turned into a zext (or sext) of the select, which is wrong
in the cases when it should have been an sext (resp. zext).  Reported
and diagnosed by Sebastien Deldon.

llvm-svn: 119728

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/2010-11-18-SelectOfExtload.ll b/llvm/test/CodeGen/X86/2010-11-18-SelectOfExtload.ll
new file mode 100644
index 00000000000..a1074b6b8f3
--- /dev/null
+++ b/llvm/test/CodeGen/X86/2010-11-18-SelectOfExtload.ll
@@ -0,0 +1,15 @@
+; RUN: llc < %s -march=x86 | FileCheck %s
+; Both values were being zero extended.
+@u = external global i8
+@s = external global i8
+define i32 @foo(i1 %cond) {
+; CHECK: @foo
+  %u_base = load i8* @u
+  %u_val = zext i8 %u_base to i32
+; CHECK: movzbl
+; CHECK: movsbl
+  %s_base = load i8* @s
+  %s_val = sext i8 %s_base to i32
+  %val = select i1 %cond, i32 %u_val, i32 %s_val
+  ret i32 %val
+}