[llvm] Mark win x64 SEH pseudo instruction as meta instructions (#110889)

When adding new SEH pseudo instructions in #110024 I noticed that some
of the tests were changing their output since these new instructions
were counting towards thresholds for branching versus folding decisions.

These instructions do not result in real machine instructions being
emitted, so they should be marked as meta instructions.

Author: dpaoliello

llvm/lib/Target/X86/X86InstrCompiler.td

@@ -235,7 +235,7 @@ let isBranch = 1, isTerminator = 1, isCodeGenOnly = 1 in {
 //===----------------------------------------------------------------------===//
 // Pseudo instructions used by unwind info.
 //
-let isPseudo = 1, SchedRW = [WriteSystem] in {
+let isPseudo = 1, isMeta = 1, SchedRW = [WriteSystem] in {
   def SEH_PushReg : I<0, Pseudo, (outs), (ins i32imm:$reg),
                             "#SEH_PushReg $reg", []>;
   def SEH_SaveReg : I<0, Pseudo, (outs), (ins i32imm:$reg, i32imm:$dst),

llvm/test/CodeGen/X86/x86-win64-shrink-wrapping.ll

@@ -17,7 +17,7 @@ define i32 @loopInfoSaveOutsideLoop(i32 %cond, i32 %N) #0 {
 ; ENABLE-NEXT:    .seh_pushreg %rbx
 ; ENABLE-NEXT:    .seh_endprologue
 ; ENABLE-NEXT:    testl %ecx, %ecx
-; ENABLE-NEXT:    je .LBB0_4
+; ENABLE-NEXT:    je .LBB0_5
 ; ENABLE-NEXT:  # %bb.1: # %for.preheader
 ; ENABLE-NEXT:    #APP
 ; ENABLE-NEXT:    nop
@@ -38,11 +38,11 @@ define i32 @loopInfoSaveOutsideLoop(i32 %cond, i32 %N) #0 {
 ; ENABLE-NEXT:    nop
 ; ENABLE-NEXT:    #NO_APP
 ; ENABLE-NEXT:    shll $3, %eax
-; ENABLE-NEXT:    jmp .LBB0_5
-; ENABLE-NEXT:  .LBB0_4: # %if.else
+; ENABLE-NEXT:    popq %rbx
+; ENABLE-NEXT:    retq
+; ENABLE-NEXT:  .LBB0_5: # %if.else
 ; ENABLE-NEXT:    movl %edx, %eax
 ; ENABLE-NEXT:    addl %edx, %eax
-; ENABLE-NEXT:  .LBB0_5: # %if.end
 ; ENABLE-NEXT:    popq %rbx
 ; ENABLE-NEXT:    retq
 ; ENABLE-NEXT:    .seh_endproc
@@ -53,7 +53,7 @@ define i32 @loopInfoSaveOutsideLoop(i32 %cond, i32 %N) #0 {
 ; DISABLE-NEXT:    .seh_pushreg %rbx
 ; DISABLE-NEXT:    .seh_endprologue
 ; DISABLE-NEXT:    testl %ecx, %ecx
-; DISABLE-NEXT:    je .LBB0_4
+; DISABLE-NEXT:    je .LBB0_5
 ; DISABLE-NEXT:  # %bb.1: # %for.preheader
 ; DISABLE-NEXT:    #APP
 ; DISABLE-NEXT:    nop
@@ -74,11 +74,11 @@ define i32 @loopInfoSaveOutsideLoop(i32 %cond, i32 %N) #0 {
 ; DISABLE-NEXT:    nop
 ; DISABLE-NEXT:    #NO_APP
 ; DISABLE-NEXT:    shll $3, %eax
-; DISABLE-NEXT:    jmp .LBB0_5
-; DISABLE-NEXT:  .LBB0_4: # %if.else
+; DISABLE-NEXT:    popq %rbx
+; DISABLE-NEXT:    retq
+; DISABLE-NEXT:  .LBB0_5: # %if.else
 ; DISABLE-NEXT:    movl %edx, %eax
 ; DISABLE-NEXT:    addl %edx, %eax
-; DISABLE-NEXT:  .LBB0_5: # %if.end
 ; DISABLE-NEXT:    popq %rbx
 ; DISABLE-NEXT:    retq
 ; DISABLE-NEXT:    .seh_endproc
@@ -157,7 +157,7 @@ define i32 @loopInfoSaveOutsideLoop2(i32 %cond, i32 %N) #0 {
 ; DISABLE-NEXT:    .seh_pushreg %rbx
 ; DISABLE-NEXT:    .seh_endprologue
 ; DISABLE-NEXT:    testl %ecx, %ecx
-; DISABLE-NEXT:    je .LBB1_4
+; DISABLE-NEXT:    je .LBB1_5
 ; DISABLE-NEXT:  # %bb.1: # %for.preheader
 ; DISABLE-NEXT:    #APP
 ; DISABLE-NEXT:    nop
@@ -178,11 +178,11 @@ define i32 @loopInfoSaveOutsideLoop2(i32 %cond, i32 %N) #0 {
 ; DISABLE-NEXT:    nop
 ; DISABLE-NEXT:    #NO_APP
 ; DISABLE-NEXT:    shll $3, %eax
-; DISABLE-NEXT:    jmp .LBB1_5
-; DISABLE-NEXT:  .LBB1_4: # %if.else
+; DISABLE-NEXT:    popq %rbx
+; DISABLE-NEXT:    retq
+; DISABLE-NEXT:  .LBB1_5: # %if.else
 ; DISABLE-NEXT:    addl %edx, %edx
 ; DISABLE-NEXT:    movl %edx, %eax
-; DISABLE-NEXT:  .LBB1_5: # %if.end
 ; DISABLE-NEXT:    popq %rbx
 ; DISABLE-NEXT:    retq
 ; DISABLE-NEXT:    .seh_endproc