X86: Add a testcase for PR25951

llvm-svn: 256801

llvm/test/CodeGen/X86/copy-eflags.ll

@@ -0,0 +1,54 @@
+; RUN: llc -o - %s | FileCheck %s
+; This tests for the problem originally reported in http://llvm.org/PR25951
+target triple = "i686-unknown-linux-gnu"
+
+@b = common global i8 0, align 1
+@c = common global i32 0, align 4
+@a = common global i8 0, align 1
+@d = common global i8 0, align 1
+@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
+
+; CHECK-LABEL: func:
+; This tests whether eax is properly saved/restored around the lahf/sahf
+; instruction sequences.
+define i32 @func() {
+entry:
+  %bval = load i8, i8* @b
+  %inc = add i8 %bval, 1
+  store i8 %inc, i8* @b
+  %cval = load i32, i32* @c
+  %inc1 = add nsw i32 %cval, 1
+  store i32 %inc1, i32* @c
+  %aval = load i8, i8* @a
+  %inc2 = add i8 %aval, 1
+  store i8 %inc2, i8* @a
+; Copy flags produced by the incb of %inc1 to a register, need to save+restore
+; eax around it. The flags will be reused by %tobool.
+; CHECK: pushl %eax
+; CHECK: seto %al
+; CHECK: lahf
+; CHECK: movl %eax, [[REG:%[a-z]+]]
+; CHECK: popl %eax
+  %cmp = icmp eq i8 %aval, %bval
+  %conv5 = zext i1 %cmp to i8
+  store i8 %conv5, i8* @d
+  %tobool = icmp eq i32 %inc1, 0
+; We restore flags with an 'addb, sahf' sequence, need to save+restore eax
+; around it.
+; CHECK: pushl %eax
+; CHECK: movl [[REG]], %eax
+; CHECK: addb $127, %al
+; CHECK: sahf
+; CHECK: popl %eax
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:
+  %conv6 = sext i8 %inc to i32
+  %call = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 %conv6)
+  br label %if.end
+
+if.end:
+  ret i32 0
+}
+
+declare i32 @printf(i8* nocapture readonly, ...)