Revert rG2149aa73f640c96 "[X86] Add support for reusing ZF etc. from locked XADD instructions (PR20841)"

This might be the cause of some msan build failures - I don't have access to a msan build right now, so this is a speculative revert.

Author: RKSimon

llvm/lib/Target/X86/X86InstrInfo.cpp

@@ -4020,12 +4020,10 @@ inline static bool isDefConvertible(const MachineInstr &MI, bool &NoSignFlag,
   case X86::SBB8ri:    case X86::SBB64rr:  case X86::SBB32rr:
   case X86::SBB16rr:   case X86::SBB8rr:   case X86::SBB64rm:
   case X86::SBB32rm:   case X86::SBB16rm:  case X86::SBB8rm:
-  case X86::NEG8r:     case X86::NEG16r:   case X86::NEG32r:  case X86::NEG64r:
-  case X86::LXADD64:   case X86::LXADD32:  case X86::LXADD16: case X86::LXADD8:
-  // TODO: Add additional LOCK/XADD instructions when we have test coverage.
-  case X86::SAR8r1:    case X86::SAR16r1:  case X86::SAR32r1: case X86::SAR64r1:
-  case X86::SHR8r1:    case X86::SHR16r1:  case X86::SHR32r1: case X86::SHR64r1:
-  case X86::SHL8r1:    case X86::SHL16r1:  case X86::SHL32r1: case X86::SHL64r1:
+  case X86::NEG8r:     case X86::NEG16r:   case X86::NEG32r: case X86::NEG64r:
+  case X86::SAR8r1:    case X86::SAR16r1:  case X86::SAR32r1:case X86::SAR64r1:
+  case X86::SHR8r1:    case X86::SHR16r1:  case X86::SHR32r1:case X86::SHR64r1:
+  case X86::SHL8r1:    case X86::SHL16r1:  case X86::SHL32r1:case X86::SHL64r1:
   case X86::LZCNT16rr: case X86::LZCNT16rm:
   case X86::LZCNT32rr: case X86::LZCNT32rm:
   case X86::LZCNT64rr: case X86::LZCNT64rm:

llvm/test/CodeGen/X86/atomic-eflags-reuse.ll

@@ -228,6 +228,7 @@ define i8 @test_add_1_cmov_cmov(i64* %p, i8* %q) #0 {
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    movl $1, %eax
 ; CHECK-NEXT:    lock xaddq %rax, (%rdi)
+; CHECK-NEXT:    testq %rax, %rax
 ; CHECK-NEXT:    movl $12, %eax
 ; CHECK-NEXT:    movl $34, %ecx
 ; CHECK-NEXT:    cmovsl %eax, %ecx

llvm/test/CodeGen/X86/atomic-flags.ll

@@ -124,13 +124,14 @@ L4:
   ret i32 4
 }
 
-; PR20841 - ensure we reuse the ZF flag from XADD for compares with zero.
+; FIXME: PR20841 - ensure we reuse the ZF flag from XADD for compares with zero.
 
 define zeroext i1 @xadd_cmp0_i64(i64* %x) nounwind {
 ; X64-LABEL: xadd_cmp0_i64:
 ; X64:       # %bb.0:
 ; X64-NEXT:    movl $1, %eax
 ; X64-NEXT:    lock xaddq %rax, (%rdi)
+; X64-NEXT:    testq %rax, %rax
 ; X64-NEXT:    sete %al
 ; X64-NEXT:    retq
 ;
@@ -166,6 +167,7 @@ define zeroext i1 @xadd_cmp0_i32(i32* %x) nounwind {
 ; X64:       # %bb.0:
 ; X64-NEXT:    movl $1, %eax
 ; X64-NEXT:    lock xaddl %eax, (%rdi)
+; X64-NEXT:    testl %eax, %eax
 ; X64-NEXT:    setne %al
 ; X64-NEXT:    retq
 ;
@@ -174,6 +176,7 @@ define zeroext i1 @xadd_cmp0_i32(i32* %x) nounwind {
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    movl $1, %ecx
 ; X86-NEXT:    lock xaddl %ecx, (%eax)
+; X86-NEXT:    testl %ecx, %ecx
 ; X86-NEXT:    setne %al
 ; X86-NEXT:    retl
   %add = atomicrmw add i32* %x, i32 1 seq_cst
@@ -186,6 +189,7 @@ define zeroext i1 @xadd_cmp0_i16(i16* %x) nounwind {
 ; X64:       # %bb.0:
 ; X64-NEXT:    movw $1, %ax
 ; X64-NEXT:    lock xaddw %ax, (%rdi)
+; X64-NEXT:    testw %ax, %ax
 ; X64-NEXT:    sete %al
 ; X64-NEXT:    retq
 ;
@@ -194,6 +198,7 @@ define zeroext i1 @xadd_cmp0_i16(i16* %x) nounwind {
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    movw $1, %cx
 ; X86-NEXT:    lock xaddw %cx, (%eax)
+; X86-NEXT:    testw %cx, %cx
 ; X86-NEXT:    sete %al
 ; X86-NEXT:    retl
   %add = atomicrmw add i16* %x, i16 1 seq_cst
@@ -206,6 +211,7 @@ define zeroext i1 @xadd_cmp0_i8(i8* %x) nounwind {
 ; X64:       # %bb.0:
 ; X64-NEXT:    movb $1, %al
 ; X64-NEXT:    lock xaddb %al, (%rdi)
+; X64-NEXT:    testb %al, %al
 ; X64-NEXT:    setne %al
 ; X64-NEXT:    retq
 ;
@@ -214,6 +220,7 @@ define zeroext i1 @xadd_cmp0_i8(i8* %x) nounwind {
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    movb $1, %cl
 ; X86-NEXT:    lock xaddb %cl, (%eax)
+; X86-NEXT:    testb %cl, %cl
 ; X86-NEXT:    setne %al
 ; X86-NEXT:    retl
   %add = atomicrmw add i8* %x, i8 1 seq_cst