Index: llvm/trunk/lib/Target/X86/X86FlagsCopyLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86FlagsCopyLowering.cpp
+++ llvm/trunk/lib/Target/X86/X86FlagsCopyLowering.cpp
@@ -97,6 +97,7 @@
 
 private:
   MachineRegisterInfo *MRI;
+  const X86Subtarget *Subtarget;
   const X86InstrInfo *TII;
   const TargetRegisterInfo *TRI;
   const TargetRegisterClass *PromoteRC;
@@ -346,10 +347,10 @@
   LLVM_DEBUG(dbgs() << "********** " << getPassName() << " : " << MF.getName()
                     << " **********\n");
 
-  auto &Subtarget = MF.getSubtarget<X86Subtarget>();
+  Subtarget = &MF.getSubtarget<X86Subtarget>();
   MRI = &MF.getRegInfo();
-  TII = Subtarget.getInstrInfo();
-  TRI = Subtarget.getRegisterInfo();
+  TII = Subtarget->getInstrInfo();
+  TRI = Subtarget->getRegisterInfo();
   MDT = &getAnalysis<MachineDominatorTree>();
   PromoteRC = &X86::GR8RegClass;
 
@@ -960,10 +961,14 @@
           .addReg(Reg)
           .addImm(SubRegIdx[OrigRegSize]);
     } else if (OrigRegSize > TargetRegSize) {
-      BuildMI(MBB, SetPos, SetLoc, TII->get(TargetOpcode::EXTRACT_SUBREG),
+      if (TargetRegSize == 1 && !Subtarget->is64Bit()) {
+        // Need to constrain the register class.
+        MRI->constrainRegClass(Reg, &X86::GR32_ABCDRegClass);
+      }
+
+      BuildMI(MBB, SetPos, SetLoc, TII->get(TargetOpcode::COPY),
               NewReg)
-          .addReg(Reg)
-          .addImm(SubRegIdx[TargetRegSize]);
+          .addReg(Reg, 0, SubRegIdx[TargetRegSize]);
     } else {
       BuildMI(MBB, SetPos, SetLoc, TII->get(TargetOpcode::COPY), NewReg)
           .addReg(Reg);
Index: llvm/trunk/test/CodeGen/X86/flags-copy-lowering.mir
===================================================================
--- llvm/trunk/test/CodeGen/X86/flags-copy-lowering.mir
+++ llvm/trunk/test/CodeGen/X86/flags-copy-lowering.mir
@@ -545,7 +545,7 @@
     MOV8mr $rsp, 1, $noreg, -16, $noreg, killed %4
   ; CHECK-NOT:     $eflags =
   ; CHECK:         %[[ZERO:[^:]*]]:gr32 = MOV32r0 implicit-def $eflags
-  ; CHECK-NEXT:    %[[ZERO_SUBREG:[^:]*]]:gr8 = EXTRACT_SUBREG %[[ZERO]], %subreg.sub_8bit
+  ; CHECK-NEXT:    %[[ZERO_SUBREG:[^:]*]]:gr8 = COPY %[[ZERO]].sub_8bit
   ; CHECK-NEXT:    %[[REPLACEMENT:[^:]*]]:gr8 = SUB8rr %[[ZERO_SUBREG]], %[[CF_REG]]
   ; CHECK-NEXT:    MOV8mr $rsp, 1, $noreg, -16, $noreg, killed %[[REPLACEMENT]]
 
@@ -554,9 +554,9 @@
     MOV16mr $rsp, 1, $noreg, -16, $noreg, killed %5
   ; CHECK-NOT:     $eflags =
   ; CHECK:         %[[CF_EXT:[^:]*]]:gr32 = MOVZX32rr8 %[[CF_REG]]
-  ; CHECK-NEXT:    %[[CF_TRUNC:[^:]*]]:gr16 = EXTRACT_SUBREG %[[CF_EXT]], %subreg.sub_16bit
+  ; CHECK-NEXT:    %[[CF_TRUNC:[^:]*]]:gr16 = COPY %[[CF_EXT]].sub_16bit
   ; CHECK-NEXT:    %[[ZERO:[^:]*]]:gr32 = MOV32r0 implicit-def $eflags
-  ; CHECK-NEXT:    %[[ZERO_SUBREG:[^:]*]]:gr16 = EXTRACT_SUBREG %[[ZERO]], %subreg.sub_16bit
+  ; CHECK-NEXT:    %[[ZERO_SUBREG:[^:]*]]:gr16 = COPY %[[ZERO]].sub_16bit
   ; CHECK-NEXT:    %[[REPLACEMENT:[^:]*]]:gr16 = SUB16rr %[[ZERO_SUBREG]], %[[CF_TRUNC]]
   ; CHECK-NEXT:    MOV16mr $rsp, 1, $noreg, -16, $noreg, killed %[[REPLACEMENT]]
 
Index: llvm/trunk/test/CodeGen/X86/pr38539.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/pr38539.ll
+++ llvm/trunk/test/CodeGen/X86/pr38539.ll
@@ -0,0 +1,314 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown -verify-machineinstrs | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=i686-unknown -verify-machineinstrs | FileCheck %s --check-prefix=X86
+
+; This test is targeted at 64-bit mode. It used to crash due to the creation of an EXTRACT_SUBREG after the peephole pass had ran.
+define void @f() {
+; X64-LABEL: f:
+; X64:       # %bb.0: # %BB
+; X64-NEXT:    pushq %rbp
+; X64-NEXT:    .cfi_def_cfa_offset 16
+; X64-NEXT:    pushq %r14
+; X64-NEXT:    .cfi_def_cfa_offset 24
+; X64-NEXT:    pushq %rbx
+; X64-NEXT:    .cfi_def_cfa_offset 32
+; X64-NEXT:    subq $16, %rsp
+; X64-NEXT:    .cfi_def_cfa_offset 48
+; X64-NEXT:    .cfi_offset %rbx, -32
+; X64-NEXT:    .cfi_offset %r14, -24
+; X64-NEXT:    .cfi_offset %rbp, -16
+; X64-NEXT:    movzbl {{[0-9]+}}(%rsp), %ebx
+; X64-NEXT:    movq %rbx, %rcx
+; X64-NEXT:    shlq $62, %rcx
+; X64-NEXT:    sarq $62, %rcx
+; X64-NEXT:    movq (%rsp), %r14
+; X64-NEXT:    movb (%rax), %bpl
+; X64-NEXT:    xorl %edi, %edi
+; X64-NEXT:    xorl %esi, %esi
+; X64-NEXT:    movq %r14, %rdx
+; X64-NEXT:    callq __modti3
+; X64-NEXT:    andl $3, %edx
+; X64-NEXT:    cmpq %rax, %r14
+; X64-NEXT:    sbbq %rdx, %rbx
+; X64-NEXT:    setb %sil
+; X64-NEXT:    setae %bl
+; X64-NEXT:    testb %al, %al
+; X64-NEXT:    setne %dl
+; X64-NEXT:    setne (%rax)
+; X64-NEXT:    movzbl %bpl, %eax
+; X64-NEXT:    xorl %ecx, %ecx
+; X64-NEXT:    subb %sil, %cl
+; X64-NEXT:    # kill: def $eax killed $eax def $ax
+; X64-NEXT:    divb %al
+; X64-NEXT:    negb %bl
+; X64-NEXT:    cmpb %al, %al
+; X64-NEXT:    setle %al
+; X64-NEXT:    negb %al
+; X64-NEXT:    cbtw
+; X64-NEXT:    idivb %bl
+; X64-NEXT:    movsbl %ah, %eax
+; X64-NEXT:    movzbl %al, %eax
+; X64-NEXT:    andl $1, %eax
+; X64-NEXT:    shlq $4, %rax
+; X64-NEXT:    negq %rax
+; X64-NEXT:    negb %dl
+; X64-NEXT:    leaq -16(%rsp,%rax), %rax
+; X64-NEXT:    movq %rax, (%rax)
+; X64-NEXT:    movl %ecx, %eax
+; X64-NEXT:    cbtw
+; X64-NEXT:    idivb %dl
+; X64-NEXT:    movsbl %ah, %eax
+; X64-NEXT:    andb $1, %al
+; X64-NEXT:    movb %al, (%rax)
+; X64-NEXT:    addq $16, %rsp
+; X64-NEXT:    .cfi_def_cfa_offset 32
+; X64-NEXT:    popq %rbx
+; X64-NEXT:    .cfi_def_cfa_offset 24
+; X64-NEXT:    popq %r14
+; X64-NEXT:    .cfi_def_cfa_offset 16
+; X64-NEXT:    popq %rbp
+; X64-NEXT:    .cfi_def_cfa_offset 8
+; X64-NEXT:    retq
+;
+; X86-LABEL: f:
+; X86:       # %bb.0: # %BB
+; X86-NEXT:    pushl %ebp
+; X86-NEXT:    .cfi_def_cfa_offset 8
+; X86-NEXT:    .cfi_offset %ebp, -8
+; X86-NEXT:    movl %esp, %ebp
+; X86-NEXT:    .cfi_def_cfa_register %ebp
+; X86-NEXT:    pushl %ebx
+; X86-NEXT:    pushl %edi
+; X86-NEXT:    pushl %esi
+; X86-NEXT:    andl $-8, %esp
+; X86-NEXT:    subl $48, %esp
+; X86-NEXT:    .cfi_offset %esi, -20
+; X86-NEXT:    .cfi_offset %edi, -16
+; X86-NEXT:    .cfi_offset %ebx, -12
+; X86-NEXT:    movzbl {{[0-9]+}}(%esp), %esi
+; X86-NEXT:    movl %esi, %eax
+; X86-NEXT:    shll $30, %eax
+; X86-NEXT:    movl %eax, %ecx
+; X86-NEXT:    sarl $30, %ecx
+; X86-NEXT:    sarl $31, %eax
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %edi
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %ebx
+; X86-NEXT:    movb (%eax), %dl
+; X86-NEXT:    movb %dl, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
+; X86-NEXT:    leal {{[0-9]+}}(%esp), %edx
+; X86-NEXT:    pushl %eax
+; X86-NEXT:    pushl %ecx
+; X86-NEXT:    pushl %ebx
+; X86-NEXT:    pushl %edi
+; X86-NEXT:    pushl $0
+; X86-NEXT:    pushl $0
+; X86-NEXT:    pushl $0
+; X86-NEXT:    pushl $0
+; X86-NEXT:    pushl %edx
+; X86-NEXT:    calll __modti3
+; X86-NEXT:    addl $32, %esp
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    andl $3, %eax
+; X86-NEXT:    xorl %ecx, %ecx
+; X86-NEXT:    cmpl {{[0-9]+}}(%esp), %edi
+; X86-NEXT:    sbbl {{[0-9]+}}(%esp), %ebx
+; X86-NEXT:    sbbl %eax, %esi
+; X86-NEXT:    sbbl $0, %ecx
+; X86-NEXT:    setae %dl
+; X86-NEXT:    sbbb %cl, %cl
+; X86-NEXT:    testb %al, %al
+; X86-NEXT:    setne %ch
+; X86-NEXT:    setne (%eax)
+; X86-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %dh # 1-byte Reload
+; X86-NEXT:    movzbl %dh, %eax
+; X86-NEXT:    # kill: def $eax killed $eax def $ax
+; X86-NEXT:    divb %dh
+; X86-NEXT:    negb %ch
+; X86-NEXT:    negb %dl
+; X86-NEXT:    cmpb %al, %al
+; X86-NEXT:    setle %al
+; X86-NEXT:    negb %al
+; X86-NEXT:    cbtw
+; X86-NEXT:    idivb %dl
+; X86-NEXT:    movsbl %ah, %eax
+; X86-NEXT:    movzbl %al, %eax
+; X86-NEXT:    andl $1, %eax
+; X86-NEXT:    negl %eax
+; X86-NEXT:    leal (%eax,%eax,2), %eax
+; X86-NEXT:    leal -4(%esp,%eax,4), %eax
+; X86-NEXT:    movl %eax, (%eax)
+; X86-NEXT:    movl %ecx, %eax
+; X86-NEXT:    cbtw
+; X86-NEXT:    idivb %ch
+; X86-NEXT:    movsbl %ah, %eax
+; X86-NEXT:    andb $1, %al
+; X86-NEXT:    movb %al, (%eax)
+; X86-NEXT:    leal -12(%ebp), %esp
+; X86-NEXT:    popl %esi
+; X86-NEXT:    popl %edi
+; X86-NEXT:    popl %ebx
+; X86-NEXT:    popl %ebp
+; X86-NEXT:    .cfi_def_cfa %esp, 4
+; X86-NEXT:    retl
+BB:
+  %A30 = alloca i66
+  %L17 = load i66, i66* %A30
+  %B20 = and i66 %L17, -1
+  %G2 = getelementptr i66, i66* %A30, i1 true
+  %L10 = load i8, i8* undef
+  %B6 = udiv i8 %L10, %L10
+  %C15 = icmp eq i8 undef, 0
+  %B8 = srem i66 0, %B20
+  %C2 = icmp ule i66 %B8, %B20
+  %B5 = or i8 0, %B6
+  %C19 = icmp uge i1 false, %C2
+  %C1 = icmp sle i8 undef, %B5
+  %B37 = srem i1 %C1, %C2
+  %C7 = icmp uge i1 false, %C15
+  store i1 %C7, i1* undef
+  %G6 = getelementptr i66, i66* %G2, i1 %B37
+  store i66* %G6, i66** undef
+  %B30 = srem i1 %C19, %C7
+  store i1 %B30, i1* undef
+  ret void
+}
+
+; Similar to above, but bitwidth adjusted to target 32-bit mode. This also shows that we didn't constrain the register class when extracting a subreg.
+define void @g() {
+; X64-LABEL: g:
+; X64:       # %bb.0: # %BB
+; X64-NEXT:    movl -{{[0-9]+}}(%rsp), %eax
+; X64-NEXT:    movzbl -{{[0-9]+}}(%rsp), %esi
+; X64-NEXT:    shlq $32, %rsi
+; X64-NEXT:    orq %rax, %rsi
+; X64-NEXT:    movq %rsi, %rdi
+; X64-NEXT:    shlq $30, %rdi
+; X64-NEXT:    sarq $30, %rdi
+; X64-NEXT:    movb (%rax), %al
+; X64-NEXT:    movzbl %al, %eax
+; X64-NEXT:    # kill: def $eax killed $eax def $ax
+; X64-NEXT:    divb %al
+; X64-NEXT:    movl %eax, %r8d
+; X64-NEXT:    xorl %eax, %eax
+; X64-NEXT:    xorl %edx, %edx
+; X64-NEXT:    idivq %rdi
+; X64-NEXT:    movabsq $17179869183, %rax # imm = 0x3FFFFFFFF
+; X64-NEXT:    andq %rdx, %rax
+; X64-NEXT:    testb %al, %al
+; X64-NEXT:    setne %dil
+; X64-NEXT:    setne (%rax)
+; X64-NEXT:    cmpq %rsi, %rax
+; X64-NEXT:    seta %dl
+; X64-NEXT:    setbe %cl
+; X64-NEXT:    negb %cl
+; X64-NEXT:    cmpb %r8b, %al
+; X64-NEXT:    setle %al
+; X64-NEXT:    negb %al
+; X64-NEXT:    cbtw
+; X64-NEXT:    idivb %cl
+; X64-NEXT:    movsbl %ah, %eax
+; X64-NEXT:    movzbl %al, %eax
+; X64-NEXT:    andl $1, %eax
+; X64-NEXT:    shlq $3, %rax
+; X64-NEXT:    negq %rax
+; X64-NEXT:    negb %dil
+; X64-NEXT:    negb %dl
+; X64-NEXT:    leaq -16(%rsp,%rax), %rax
+; X64-NEXT:    movq %rax, (%rax)
+; X64-NEXT:    movl %edx, %eax
+; X64-NEXT:    cbtw
+; X64-NEXT:    idivb %dil
+; X64-NEXT:    movsbl %ah, %eax
+; X64-NEXT:    andb $1, %al
+; X64-NEXT:    movb %al, (%rax)
+; X64-NEXT:    retq
+;
+; X86-LABEL: g:
+; X86:       # %bb.0: # %BB
+; X86-NEXT:    pushl %ebp
+; X86-NEXT:    .cfi_def_cfa_offset 8
+; X86-NEXT:    .cfi_offset %ebp, -8
+; X86-NEXT:    movl %esp, %ebp
+; X86-NEXT:    .cfi_def_cfa_register %ebp
+; X86-NEXT:    pushl %ebx
+; X86-NEXT:    pushl %edi
+; X86-NEXT:    pushl %esi
+; X86-NEXT:    andl $-8, %esp
+; X86-NEXT:    subl $16, %esp
+; X86-NEXT:    .cfi_offset %esi, -20
+; X86-NEXT:    .cfi_offset %edi, -16
+; X86-NEXT:    .cfi_offset %ebx, -12
+; X86-NEXT:    movzbl {{[0-9]+}}(%esp), %esi
+; X86-NEXT:    movl %esi, %eax
+; X86-NEXT:    shll $30, %eax
+; X86-NEXT:    sarl $30, %eax
+; X86-NEXT:    movl (%esp), %edi
+; X86-NEXT:    movb (%eax), %bl
+; X86-NEXT:    pushl %eax
+; X86-NEXT:    pushl %edi
+; X86-NEXT:    pushl $0
+; X86-NEXT:    pushl $0
+; X86-NEXT:    calll __moddi3
+; X86-NEXT:    addl $16, %esp
+; X86-NEXT:    andl $3, %edx
+; X86-NEXT:    cmpl %eax, %edi
+; X86-NEXT:    sbbl %edx, %esi
+; X86-NEXT:    setb %dl
+; X86-NEXT:    setae %dh
+; X86-NEXT:    testb %al, %al
+; X86-NEXT:    setne %bh
+; X86-NEXT:    setne (%eax)
+; X86-NEXT:    movzbl %bl, %eax
+; X86-NEXT:    xorl %ecx, %ecx
+; X86-NEXT:    subb %dl, %cl
+; X86-NEXT:    # kill: def $eax killed $eax def $ax
+; X86-NEXT:    divb %bl
+; X86-NEXT:    negb %dh
+; X86-NEXT:    cmpb %al, %al
+; X86-NEXT:    setle %al
+; X86-NEXT:    negb %al
+; X86-NEXT:    cbtw
+; X86-NEXT:    idivb %dh
+; X86-NEXT:    movsbl %ah, %eax
+; X86-NEXT:    movzbl %al, %eax
+; X86-NEXT:    andl $1, %eax
+; X86-NEXT:    shll $3, %eax
+; X86-NEXT:    negl %eax
+; X86-NEXT:    negb %bh
+; X86-NEXT:    leal -8(%esp,%eax), %eax
+; X86-NEXT:    movl %eax, (%eax)
+; X86-NEXT:    movl %ecx, %eax
+; X86-NEXT:    cbtw
+; X86-NEXT:    idivb %bh
+; X86-NEXT:    movsbl %ah, %eax
+; X86-NEXT:    andb $1, %al
+; X86-NEXT:    movb %al, (%eax)
+; X86-NEXT:    leal -12(%ebp), %esp
+; X86-NEXT:    popl %esi
+; X86-NEXT:    popl %edi
+; X86-NEXT:    popl %ebx
+; X86-NEXT:    popl %ebp
+; X86-NEXT:    .cfi_def_cfa %esp, 4
+; X86-NEXT:    retl
+BB:
+  %A30 = alloca i34
+  %L17 = load i34, i34* %A30
+  %B20 = and i34 %L17, -1
+  %G2 = getelementptr i34, i34* %A30, i1 true
+  %L10 = load i8, i8* undef
+  %B6 = udiv i8 %L10, %L10
+  %C15 = icmp eq i8 undef, 0
+  %B8 = srem i34 0, %B20
+  %C2 = icmp ule i34 %B8, %B20
+  %B5 = or i8 0, %B6
+  %C19 = icmp uge i1 false, %C2
+  %C1 = icmp sle i8 undef, %B5
+  %B37 = srem i1 %C1, %C2
+  %C7 = icmp uge i1 false, %C15
+  store i1 %C7, i1* undef
+  %G6 = getelementptr i34, i34* %G2, i1 %B37
+  store i34* %G6, i34** undef
+  %B30 = srem i1 %C19, %C7
+  store i1 %B30, i1* undef
+  ret void
+}