[X86] Add a test to reveal a bug in CMOV conversion.

[tianqing]

Summary

CMOV conversion first rewrites all CMOVs with memory load to branches.
Then runs a second pass to convert other CMOVs in loops if profitable.
But the first pass doesn't add new basic blocks to MachineLoopInfo,
CMOVs in these blocks are ignored in the subsequent pass.

[pengfei]

LGTM.

llvm/test/CodeGen/X86/x86-cmov-converter.ll

 ; CHECK-NOT:     cmov
 ; CHECK:         ja [[FALSE_BB:.*]]
 ; CHECK:         movl (%r{{..}}), %eax
 ; CHECK:       [[FALSE_BB]]:
 ; CHECK:         retq
   ret i32 %r
 }
 
+@begin = external global i32*
+@end = external global i32*
+
+define void @test_memoperand_loop(i32 %data) #0 {
+; CHECK-LABEL: test_memoperand_loop:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    movq begin@GOTPCREL(%rip), %r8
+; CHECK-NEXT:    movq (%r8), %rax
+; CHECK-NEXT:    movq end@GOTPCREL(%rip), %rcx
+; CHECK-NEXT:    movq (%rcx), %rdx
+; CHECK-NEXT:    xorl %esi, %esi
+; CHECK-NEXT:    movq %rax, %rcx
+entry:
+  %begin = load i32*, i32** @begin, align 8
+  %end = load i32*, i32** @end, align 8
+  br label %loop.body
+
+; CHECK-NEXT:  .LBB13_1: # %loop.body
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    addq $8, %rcx
+; CHECK-NEXT:    cmpq %rdx, %rcx
+; CHECK-NEXT:    ja .LBB13_3
+; CHECK-NEXT:  # %bb.2: # %loop.body
+; CHECK-NEXT:    # in Loop: Header=BB13_1 Depth=1
+; CHECK-NEXT:    movq (%r8), %rcx
+; CHECK-NEXT:  .LBB13_3: # %loop.body
+; CHECK-NEXT:    # in Loop: Header=BB13_1 Depth=1
+; CHECK-NEXT:    movl %edi, (%rcx)
+; CHECK-NEXT:    addq $8, %rcx
+; CHECK-NEXT:    cmpq %rdx, %rcx
+; CHECK-NEXT:    cmovbeq %rax, %rcx
+; CHECK-NEXT:    movl %edi, (%rcx)
+; CHECK-NEXT:    addl $1, %esi
+; CHECK-NEXT:    cmpl $1024, %esi # imm = 0x400
+; CHECK-NEXT:    jl .LBB13_1
+loop.body:
+  %phi.iv = phi i32 [ 0, %entry ], [ %iv.next, %loop.body ]
+  %phi.ptr = phi i32* [ %begin, %entry ], [ %dst2, %loop.body ]
+  %gep1 = getelementptr inbounds i32, i32 *%phi.ptr, i64 2
+  %cmp1 = icmp ugt i32* %gep1, %end
+  %begin_dup = load i32*, i32** @begin, align 8
+  %dst1 = select i1 %cmp1, i32* %gep1, i32* %begin_dup
+  store i32 %data, i32 *%dst1, align 4
+  %gep2 = getelementptr inbounds i32, i32 *%dst1, i64 2
+  %cmp2 = icmp ugt i32* %gep2, %end
+  %dst2 = select i1 %cmp2, i32* %gep2, i32* %begin
+  store i32 %data, i32 *%dst2, align 4
+  %iv.next = add i32 %phi.iv, 1
+  %cond = icmp slt i32 %iv.next, 1024
+  br i1 %cond, label %loop.body, label %exit
+
+; CHECK-NEXT:  # %bb.4: # %exit
+; CHECK-NEXT:    retq
+exit:
+  ret void
+}
+
 attributes #0 = {"target-cpu"="x86-64"}