Fix the x86 test-shrink optimization so that it doesn't shrink comparisons

when one of the bits being tested would end up being the sign bit in the
narrower type, and a signed comparison is being performed, since this would
change the result of the signed comparison. This fixes PR5132.

llvm-svn: 83670

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/test-shrink-bug.ll b/llvm/test/CodeGen/X86/test-shrink-bug.ll
new file mode 100644
index 00000000000..64631ea5fc9
--- /dev/null
+++ b/llvm/test/CodeGen/X86/test-shrink-bug.ll
@@ -0,0 +1,23 @@
+; RUN: llc < %s | FileCheck %s
+
+; Codegen shouldn't reduce the comparison down to testb $-1, %al
+; because that changes the result of the signed test.
+; PR5132
+; CHECK: testw  $255, %ax
+
+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-f80:128:128"
+target triple = "i386-apple-darwin10.0"
+
+@g_14 = global i8 -6, align 1                     ; <i8*> [#uses=1]
+
+declare i32 @func_16(i8 signext %p_19, i32 %p_20) nounwind
+
+define i32 @func_35(i64 %p_38) nounwind ssp {
+entry:
+  %tmp = load i8* @g_14                           ; <i8> [#uses=2]
+  %conv = zext i8 %tmp to i32                     ; <i32> [#uses=1]
+  %cmp = icmp sle i32 1, %conv                    ; <i1> [#uses=1]
+  %conv2 = zext i1 %cmp to i32                    ; <i32> [#uses=1]
+  %call = call i32 @func_16(i8 signext %tmp, i32 %conv2) ssp ; <i32> [#uses=1]
+  ret i32 1
+}