X86 cmp lowering is looking past truncate on the condition node. It should only

do so when the high bits are known zero. This caused a subtle miscompilation.

rdar://12027825 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161451 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 36 insertions, 0 deletions

diff --git a/test/CodeGen/X86/2012-08-07-CmpISelBug.ll b/test/CodeGen/X86/2012-08-07-CmpISelBug.ll
new file mode 100644
index 0000000..000b853
--- /dev/null
+++ b/test/CodeGen/X86/2012-08-07-CmpISelBug.ll
@@ -0,0 +1,36 @@
+; RUN: llc < %s -mtriple=x86_64-apple-macosx | FileCheck %s
+
+; Cmp lowering should not look past the truncate unless the high bits are known
+; zero.
+; rdar://12027825
+
+define void @foo(i8 %arg4, i32 %arg5, i32* %arg14) nounwind {
+bb:
+; CHECK: foo:
+; CHECK-NOT: testl
+; CHECK: testb
+  %tmp48 = zext i8 %arg4 to i32
+  %tmp49 = and i32 %tmp48, 32
+  %tmp50 = add i32 %tmp49, 1593371643
+  %tmp55 = sub i32 %tmp50, 0
+  %tmp56 = add i32 %tmp55, 7787538
+  %tmp57 = xor i32 %tmp56, 1601159181
+  %tmp58 = xor i32 %arg5, 1601159181
+  %tmp59 = and i32 %tmp57, %tmp58
+  %tmp60 = add i32 %tmp59, -1263900958
+  %tmp67 = sub i32 %tmp60, 0
+  %tmp103 = xor i32 %tmp56, 13
+  %tmp104 = trunc i32 %tmp103 to i8
+  %tmp105 = sub i8 0, %tmp104
+  %tmp106 = add i8 %tmp105, -103
+  %tmp113 = sub i8 %tmp106, 0
+  %tmp114 = add i8 %tmp113, -72
+  %tmp141 = icmp ne i32 %tmp67, -1263900958
+  %tmp142 = select i1 %tmp141, i8 %tmp114, i8 undef
+  %tmp143 = xor i8 %tmp142, 81
+  %tmp144 = zext i8 %tmp143 to i32
+  %tmp145 = add i32 %tmp144, 2062143348
+  %tmp152 = sub i32 %tmp145, 0
+  store i32 %tmp152, i32* %arg14
+  ret void
+}