[llvm] r328929 - [X86] Add test case to show failure to promote i16 subtract when the LHS is a load and the result is stored to a different address.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Sat Mar 31 23:29:27 2018
New Revision: 328929

URL: http://llvm.org/viewvc/llvm-project?rev=328929&view=rev
Log:
[X86] Add test case to show failure to promote i16 subtract when the LHS is a load and the result is stored to a different address.

We mistakenly believe we might be able to fold this as a RMW operation, but that doesn't end up happening.

Modified:
    llvm/trunk/test/CodeGen/X86/promote-i16.ll

Modified: llvm/trunk/test/CodeGen/X86/promote-i16.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/promote-i16.ll?rev=328929&r1=328928&r2=328929&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/promote-i16.ll (original)
+++ llvm/trunk/test/CodeGen/X86/promote-i16.ll Sat Mar 31 23:29:27 2018
@@ -57,3 +57,26 @@ entry:
   %sub = sub i16 %0, %y
   ret i16 %sub
 }
+
+define void @bat(i16* %a, i16* %x, i16 signext %y) nounwind {
+; X86-LABEL: bat:
+; X86:       # %bb.0: # %entry
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT:    movzwl (%ecx), %ecx
+; X86-NEXT:    subw {{[0-9]+}}(%esp), %cx
+; X86-NEXT:    movw %cx, (%eax)
+; X86-NEXT:    retl
+;
+; X64-LABEL: bat:
+; X64:       # %bb.0: # %entry
+; X64-NEXT:    movzwl (%rsi), %eax
+; X64-NEXT:    subw %dx, %ax
+; X64-NEXT:    movw %ax, (%rdi)
+; X64-NEXT:    retq
+entry:
+  %0 = load i16, i16* %x
+  %sub = sub i16 %0, %y
+  store i16 %sub, i16* %a
+  ret void
+}