Revert "[X86][APX] Support peephole optimization with CCMP instruction (llvm#129994)"

This reverts commit 7ae7585.

There is a problem with peephole optimization for CCMP instruction. See the
example as below:
C source code:
`
  if (a > 2 || (b && (a == 2))) { … }
`
MIR before peephole optimization:
`
  TEST8rr %21:gr8, %21:gr8, implicit-def $eflags // b
  CCMP32ri %30:gr32, 2, 0, 5, implicit-def $eflags, implicit $eflags // a == 2
  CCMP32ri %30:gr32, 3, 0, 5, implicit-def $eflags, implicit $eflags // a > 3
  JCC_1 %bb.6, 2, implicit $eflags
  JMP_1 %bb.3
`
Inputs:
`
  a = 1, b = 0.
`
With the inputs above, the expected behavior is to jump to %bb.6 BB. After
TEST8rr instruction being executed with b(%21) == 0, the ZF bit is set to 1 in
eflags, so the eflags doesn't satisfy SCC condition in the following CCMP32ri
instruction (for a==2 condition) which skips compare a(%30) with 2 and
set flags in its payload to 0x202 (ZF = 0). The eflags satisfies the SCC
condition in the 2nd CCMP32ri instruction which compares a(%30) with 3. It sets
CF to 1 in eflags and the JCC instruction jumps to %bb.6 BB.

But after adding CCMP support, peephole optimization eliminates the 2nd
CCMP32ri instruction and updates the condition of JCC instruction to "BE" from
"B". With same inputs, JCC instruction will fall through to the next
instruction. It's not expected and the peephole optimization for CCMP
instruction is not correct.
`
  TEST8rr %21:gr8, %21:gr8, implicit-def $eflags // b
  CCMP32ri %30:gr32, 2, 0, 5, implicit-def $eflags, implicit $eflags  // a == 2
  JCC_1 %bb.6, 6, implicit $eflags
  JMP_1 %bb.3
`

Author: fzou1

llvm/lib/Target/X86/X86InstrConditionalCompare.td

@@ -36,7 +36,7 @@ class Ctest<bits<8> o, Format f, X86TypeInfo t, DAGOperand op1, DAGOperand op2>:
 //===----------------------------------------------------------------------===//
 // CCMP Instructions
 //
-let SchedRW = [WriteALU], isCompare = 1 in {
+let SchedRW = [WriteALU] in {
   def CCMP8rr : Ccmp<0x38, MRMDestReg, Xi8,  GR8,  GR8>;
   def CCMP16rr: Ccmp<0x39, MRMDestReg, Xi16, GR16, GR16>, PD;
   def CCMP32rr: Ccmp<0x39, MRMDestReg, Xi32, GR32, GR32>;
@@ -55,7 +55,7 @@ let SchedRW = [WriteALU], isCompare = 1 in {
   def CCMP64ri32: Ccmp<0x81, MRM7r, Xi64, GR64, i64i32imm>;
 }
 
-let mayLoad = 1, isCompare = 1 in {
+let mayLoad = 1 in {
   let SchedRW = [WriteALU.Folded] in {
     def CCMP16mi8: Ccmp<0x83, MRM7m, Xi16, i16mem, i16i8imm>, PD;
     def CCMP32mi8: Ccmp<0x83, MRM7m, Xi32, i32mem, i32i8imm>;

llvm/lib/Target/X86/X86InstrInfo.cpp

@@ -4875,10 +4875,6 @@ bool X86InstrInfo::analyzeCompare(const MachineInstr &MI, Register &SrcReg,
   case X86::CMP32ri:
   case X86::CMP16ri:
   case X86::CMP8ri:
-  case X86::CCMP64ri32:
-  case X86::CCMP32ri:
-  case X86::CCMP16ri:
-  case X86::CCMP8ri:
     SrcReg = MI.getOperand(0).getReg();
     SrcReg2 = 0;
     if (MI.getOperand(1).isImm()) {
@@ -4976,18 +4972,6 @@ bool X86InstrInfo::isRedundantFlagInstr(const MachineInstr &FlagI,
     }
     return false;
   }
-  case X86::CCMP64ri32:
-  case X86::CCMP32ri:
-  case X86::CCMP16ri:
-  case X86::CCMP8ri: {
-    // The CCMP instruction should not be optimized if the scc/dfv in it is not
-    // same as the one in previous CCMP instruction.
-    if ((FlagI.getOpcode() != OI.getOpcode()) ||
-        (OI.getOperand(2).getImm() != FlagI.getOperand(2).getImm()) ||
-        (OI.getOperand(3).getImm() != FlagI.getOperand(3).getImm()))
-      return false;
-    [[fallthrough]];
-  }
   case X86::CMP64ri32:
   case X86::CMP32ri:
   case X86::CMP16ri:

llvm/test/CodeGen/X86/apx/ccmp.ll

@@ -1300,75 +1300,5 @@ if.end:                                           ; preds = %entry, %if.then
   ret void
 }
 
-define void @ccmp_continous_adjust_imm(i32 noundef %a, i32 noundef %b) {
-; CHECK-LABEL: ccmp_continous_adjust_imm:
-; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    cmpl $2, %edi # encoding: [0x83,0xff,0x02]
-; CHECK-NEXT:    ccmpll {dfv=} $2, %esi # encoding: [0x62,0xf4,0x04,0x0c,0x83,0xfe,0x02]
-; CHECK-NEXT:    jg .LBB31_1 # encoding: [0x7f,A]
-; CHECK-NEXT:    # fixup A - offset: 1, value: .LBB31_1-1, kind: FK_PCRel_1
-; CHECK-NEXT:  # %bb.2: # %if.then
-; CHECK-NEXT:    xorl %eax, %eax # encoding: [0x31,0xc0]
-; CHECK-NEXT:    jmp foo # TAILCALL
-; CHECK-NEXT:    # encoding: [0xeb,A]
-; CHECK-NEXT:    # fixup A - offset: 1, value: foo-1, kind: FK_PCRel_1
-; CHECK-NEXT:  .LBB31_1: # %if.end
-; CHECK-NEXT:    retq # encoding: [0xc3]
-;
-; NDD-LABEL: ccmp_continous_adjust_imm:
-; NDD:       # %bb.0: # %entry
-; NDD-NEXT:    cmpl $2, %edi # encoding: [0x83,0xff,0x02]
-; NDD-NEXT:    ccmpll {dfv=} $2, %esi # encoding: [0x62,0xf4,0x04,0x0c,0x83,0xfe,0x02]
-; NDD-NEXT:    jg .LBB31_1 # encoding: [0x7f,A]
-; NDD-NEXT:    # fixup A - offset: 1, value: .LBB31_1-1, kind: FK_PCRel_1
-; NDD-NEXT:  # %bb.2: # %if.then
-; NDD-NEXT:    xorl %eax, %eax # encoding: [0x31,0xc0]
-; NDD-NEXT:    jmp foo # TAILCALL
-; NDD-NEXT:    # encoding: [0xeb,A]
-; NDD-NEXT:    # fixup A - offset: 1, value: foo-1, kind: FK_PCRel_1
-; NDD-NEXT:  .LBB31_1: # %if.end
-; NDD-NEXT:    retq # encoding: [0xc3]
-entry:
-  %cmp = icmp slt i32 %a, 2
-  %cmp1 = icmp slt i32 %b, 2
-  %or.cond = and i1 %cmp, %cmp1
-  %cmp3 = icmp slt i32 %b, 3
-  %or.cond4 = and i1 %or.cond, %cmp3
-  br i1 %or.cond4, label %if.then, label %if.end
-
-if.then:                                          ; preds = %entry
-  tail call void (...) @foo()
-  br label %if.end
-
-if.end:                                           ; preds = %if.then, %entry
-  ret void
-}
-
-define i32 @ccmp_continous_nobranch_adjust_imm(i32 noundef %a, i32 noundef %b) {
-; CHECK-LABEL: ccmp_continous_nobranch_adjust_imm:
-; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    cmpl $2, %esi # encoding: [0x83,0xfe,0x02]
-; CHECK-NEXT:    ccmpgl {dfv=} $2, %edi # encoding: [0x62,0xf4,0x04,0x0f,0x83,0xff,0x02]
-; CHECK-NEXT:    setge %al # encoding: [0x0f,0x9d,0xc0]
-; CHECK-NEXT:    movzbl %al, %eax # encoding: [0x0f,0xb6,0xc0]
-; CHECK-NEXT:    retq # encoding: [0xc3]
-;
-; NDD-LABEL: ccmp_continous_nobranch_adjust_imm:
-; NDD:       # %bb.0: # %entry
-; NDD-NEXT:    cmpl $2, %esi # encoding: [0x83,0xfe,0x02]
-; NDD-NEXT:    ccmpgl {dfv=} $2, %edi # encoding: [0x62,0xf4,0x04,0x0f,0x83,0xff,0x02]
-; NDD-NEXT:    setge %al # encoding: [0x0f,0x9d,0xc0]
-; NDD-NEXT:    movzbl %al, %eax # encoding: [0x0f,0xb6,0xc0]
-; NDD-NEXT:    retq # encoding: [0xc3]
-entry:
-  %cmp = icmp sgt i32 %a, 1
-  %cmp1 = icmp slt i32 %b, 2
-  %cmp2 = icmp slt i32 %b, 3
-  %or1 = or i1 %cmp, %cmp1
-  %or2 = or i1 %or1, %cmp2
-  %. = zext i1 %or2 to i32
-  ret i32 %.
-}
-
 declare dso_local void @foo(...)
 declare {i64, i1} @llvm.ssub.with.overflow.i64(i64, i64) nounwind readnone