Revert "[X86][MC] Always emit `rep` prefix for `bsf`"

This reverts commit c2066d19cd. It's causing failures on the build bots.
2022-08-03 14:50:41 -07:00 · 2022-08-03 14:50:41 -07:00 · 84e9194828
parent 9ffcc85fbe
commit 84e9194828
5 changed files with 39 additions and 97 deletions
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@ -982,10 +982,6 @@ void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
          X86II::isX86_64ExtendedReg(OutMI.getOperand(2).getReg()))
        std::swap(OutMI.getOperand(1), OutMI.getOperand(2));
    }
-    // Add an REP prefix to BSF instructions so that new processors can
-    // recognize as TZCNT, which has better performance than BSF.
-    if (X86::isBSF(OutMI.getOpcode()) && !MF.getFunction().hasOptSize())
-      OutMI.setFlags(X86::IP_HAS_REPEAT);
    break;
  }
  }
--- a/llvm/test/CodeGen/X86/clz.ll
+++ b/llvm/test/CodeGen/X86/clz.ll
@ -18,13 +18,13 @@ declare i64 @llvm.ctlz.i64(i64, i1)
 define i8 @cttz_i8(i8 %x)  {
 ; X86-LABEL: cttz_i8:
 ; X86:       # %bb.0:
-; X86-NEXT:    rep bsfl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    # kill: def $al killed $al killed $eax
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: cttz_i8:
 ; X64:       # %bb.0:
-; X64-NEXT:    rep bsfl %edi, %eax
+; X64-NEXT:    bsfl %edi, %eax
 ; X64-NEXT:    # kill: def $al killed $al killed $eax
 ; X64-NEXT:    retq
 ;
@ -46,13 +46,13 @@ define i8 @cttz_i8(i8 %x)  {
 define i16 @cttz_i16(i16 %x)  {
 ; X86-LABEL: cttz_i16:
 ; X86:       # %bb.0:
-; X86-NEXT:    rep bsfl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    # kill: def $ax killed $ax killed $eax
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: cttz_i16:
 ; X64:       # %bb.0:
-; X64-NEXT:    rep bsfl %edi, %eax
+; X64-NEXT:    bsfl %edi, %eax
 ; X64-NEXT:    # kill: def $ax killed $ax killed $eax
 ; X64-NEXT:    retq
 ;
@ -74,12 +74,12 @@ define i16 @cttz_i16(i16 %x)  {
 define i32 @cttz_i32(i32 %x)  {
 ; X86-LABEL: cttz_i32:
 ; X86:       # %bb.0:
-; X86-NEXT:    rep bsfl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: cttz_i32:
 ; X64:       # %bb.0:
-; X64-NEXT:    rep bsfl %edi, %eax
+; X64-NEXT:    bsfl %edi, %eax
 ; X64-NEXT:    retq
 ;
 ; X86-CLZ-LABEL: cttz_i32:
@ -102,20 +102,20 @@ define i64 @cttz_i64(i64 %x)  {
 ; X86-NOCMOV-NEXT:    testl %eax, %eax
 ; X86-NOCMOV-NEXT:    jne .LBB3_1
 ; X86-NOCMOV-NEXT:  # %bb.2:
-; X86-NOCMOV-NEXT:    rep bsfl {{[0-9]+}}(%esp), %eax
+; X86-NOCMOV-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
 ; X86-NOCMOV-NEXT:    addl $32, %eax
 ; X86-NOCMOV-NEXT:    xorl %edx, %edx
 ; X86-NOCMOV-NEXT:    retl
 ; X86-NOCMOV-NEXT:  .LBB3_1:
-; X86-NOCMOV-NEXT:    rep bsfl %eax, %eax
+; X86-NOCMOV-NEXT:    bsfl %eax, %eax
 ; X86-NOCMOV-NEXT:    xorl %edx, %edx
 ; X86-NOCMOV-NEXT:    retl
 ;
 ; X86-CMOV-LABEL: cttz_i64:
 ; X86-CMOV:       # %bb.0:
 ; X86-CMOV-NEXT:    movl {{[0-9]+}}(%esp), %ecx
-; X86-CMOV-NEXT:    rep bsfl %ecx, %edx
-; X86-CMOV-NEXT:    rep bsfl {{[0-9]+}}(%esp), %eax
+; X86-CMOV-NEXT:    bsfl %ecx, %edx
+; X86-CMOV-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
 ; X86-CMOV-NEXT:    addl $32, %eax
 ; X86-CMOV-NEXT:    testl %ecx, %ecx
 ; X86-CMOV-NEXT:    cmovnel %edx, %eax
@ -124,7 +124,7 @@ define i64 @cttz_i64(i64 %x)  {
 ;
 ; X64-LABEL: cttz_i64:
 ; X64:       # %bb.0:
-; X64-NEXT:    rep bsfq %rdi, %rax
+; X64-NEXT:    bsfq %rdi, %rax
 ; X64-NEXT:    retq
 ;
 ; X86-CLZ-LABEL: cttz_i64:
@ -519,7 +519,7 @@ define i8 @cttz_i8_zero_test(i8 %n) {
 ; X86-NEXT:    je .LBB12_1
 ; X86-NEXT:  # %bb.2: # %cond.false
 ; X86-NEXT:    movzbl %al, %eax
-; X86-NEXT:    rep bsfl %eax, %eax
+; X86-NEXT:    bsfl %eax, %eax
 ; X86-NEXT:    # kill: def $al killed $al killed $eax
 ; X86-NEXT:    retl
 ; X86-NEXT:  .LBB12_1:
@ -533,7 +533,7 @@ define i8 @cttz_i8_zero_test(i8 %n) {
 ; X64-NEXT:    je .LBB12_1
 ; X64-NEXT:  # %bb.2: # %cond.false
 ; X64-NEXT:    movzbl %dil, %eax
-; X64-NEXT:    rep bsfl %eax, %eax
+; X64-NEXT:    bsfl %eax, %eax
 ; X64-NEXT:    # kill: def $al killed $al killed $eax
 ; X64-NEXT:    retq
 ; X64-NEXT:  .LBB12_1:
@ -567,7 +567,7 @@ define i16 @cttz_i16_zero_test(i16 %n) {
 ; X86-NEXT:    testw %ax, %ax
 ; X86-NEXT:    je .LBB13_1
 ; X86-NEXT:  # %bb.2: # %cond.false
-; X86-NEXT:    rep bsfl %eax, %eax
+; X86-NEXT:    bsfl %eax, %eax
 ; X86-NEXT:    # kill: def $ax killed $ax killed $eax
 ; X86-NEXT:    retl
 ; X86-NEXT:  .LBB13_1:
@ -580,7 +580,7 @@ define i16 @cttz_i16_zero_test(i16 %n) {
 ; X64-NEXT:    testw %di, %di
 ; X64-NEXT:    je .LBB13_1
 ; X64-NEXT:  # %bb.2: # %cond.false
-; X64-NEXT:    rep bsfl %edi, %eax
+; X64-NEXT:    bsfl %edi, %eax
 ; X64-NEXT:    # kill: def $ax killed $ax killed $eax
 ; X64-NEXT:    retq
 ; X64-NEXT:  .LBB13_1:
@ -614,7 +614,7 @@ define i32 @cttz_i32_zero_test(i32 %n) {
 ; X86-NEXT:    testl %eax, %eax
 ; X86-NEXT:    je .LBB14_1
 ; X86-NEXT:  # %bb.2: # %cond.false
-; X86-NEXT:    rep bsfl %eax, %eax
+; X86-NEXT:    bsfl %eax, %eax
 ; X86-NEXT:    retl
 ; X86-NEXT:  .LBB14_1:
 ; X86-NEXT:    movl $32, %eax
@ -625,7 +625,7 @@ define i32 @cttz_i32_zero_test(i32 %n) {
 ; X64-NEXT:    testl %edi, %edi
 ; X64-NEXT:    je .LBB14_1
 ; X64-NEXT:  # %bb.2: # %cond.false
-; X64-NEXT:    rep bsfl %edi, %eax
+; X64-NEXT:    bsfl %edi, %eax
 ; X64-NEXT:    retq
 ; X64-NEXT:  .LBB14_1:
 ; X64-NEXT:    movl $32, %eax
@ -649,7 +649,7 @@ define i64 @cttz_i64_zero_test(i64 %n) {
 ; X86-NOCMOV-LABEL: cttz_i64_zero_test:
 ; X86-NOCMOV:       # %bb.0:
 ; X86-NOCMOV-NEXT:    movl {{[0-9]+}}(%esp), %ecx
-; X86-NOCMOV-NEXT:    rep bsfl {{[0-9]+}}(%esp), %edx
+; X86-NOCMOV-NEXT:    bsfl {{[0-9]+}}(%esp), %edx
 ; X86-NOCMOV-NEXT:    movl $32, %eax
 ; X86-NOCMOV-NEXT:    je .LBB15_2
 ; X86-NOCMOV-NEXT:  # %bb.1:
@ -662,18 +662,18 @@ define i64 @cttz_i64_zero_test(i64 %n) {
 ; X86-NOCMOV-NEXT:    xorl %edx, %edx
 ; X86-NOCMOV-NEXT:    retl
 ; X86-NOCMOV-NEXT:  .LBB15_3:
-; X86-NOCMOV-NEXT:    rep bsfl %ecx, %eax
+; X86-NOCMOV-NEXT:    bsfl %ecx, %eax
 ; X86-NOCMOV-NEXT:    xorl %edx, %edx
 ; X86-NOCMOV-NEXT:    retl
 ;
 ; X86-CMOV-LABEL: cttz_i64_zero_test:
 ; X86-CMOV:       # %bb.0:
 ; X86-CMOV-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-CMOV-NEXT:    rep bsfl {{[0-9]+}}(%esp), %ecx
+; X86-CMOV-NEXT:    bsfl {{[0-9]+}}(%esp), %ecx
 ; X86-CMOV-NEXT:    movl $32, %edx
 ; X86-CMOV-NEXT:    cmovnel %ecx, %edx
 ; X86-CMOV-NEXT:    addl $32, %edx
-; X86-CMOV-NEXT:    rep bsfl %eax, %eax
+; X86-CMOV-NEXT:    bsfl %eax, %eax
 ; X86-CMOV-NEXT:    cmovel %edx, %eax
 ; X86-CMOV-NEXT:    xorl %edx, %edx
 ; X86-CMOV-NEXT:    retl
@ -683,7 +683,7 @@ define i64 @cttz_i64_zero_test(i64 %n) {
 ; X64-NEXT:    testq %rdi, %rdi
 ; X64-NEXT:    je .LBB15_1
 ; X64-NEXT:  # %bb.2: # %cond.false
-; X64-NEXT:    rep bsfq %rdi, %rax
+; X64-NEXT:    bsfq %rdi, %rax
 ; X64-NEXT:    retq
 ; X64-NEXT:  .LBB15_1:
 ; X64-NEXT:    movl $64, %eax
@ -833,7 +833,7 @@ define i8 @cttz_i8_knownbits(i8 %x)  {
 ; X86-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    orb $2, %al
 ; X86-NEXT:    movzbl %al, %eax
-; X86-NEXT:    rep bsfl %eax, %eax
+; X86-NEXT:    bsfl %eax, %eax
 ; X86-NEXT:    # kill: def $al killed $al killed $eax
 ; X86-NEXT:    retl
 ;
@ -841,7 +841,7 @@ define i8 @cttz_i8_knownbits(i8 %x)  {
 ; X64:       # %bb.0:
 ; X64-NEXT:    orb $2, %dil
 ; X64-NEXT:    movzbl %dil, %eax
-; X64-NEXT:    rep bsfl %eax, %eax
+; X64-NEXT:    bsfl %eax, %eax
 ; X64-NEXT:    # kill: def $al killed $al killed $eax
 ; X64-NEXT:    retq
 ;
@ -994,12 +994,12 @@ define i64 @cttz_i64_zero_test_knownneverzero(i64 %n) {
 ; X86-NOCMOV-NEXT:  # %bb.2:
 ; X86-NOCMOV-NEXT:    movl $-2147483648, %eax # imm = 0x80000000
 ; X86-NOCMOV-NEXT:    orl {{[0-9]+}}(%esp), %eax
-; X86-NOCMOV-NEXT:    rep bsfl %eax, %eax
+; X86-NOCMOV-NEXT:    bsfl %eax, %eax
 ; X86-NOCMOV-NEXT:    orl $32, %eax
 ; X86-NOCMOV-NEXT:    xorl %edx, %edx
 ; X86-NOCMOV-NEXT:    retl
 ; X86-NOCMOV-NEXT:  .LBB22_1:
-; X86-NOCMOV-NEXT:    rep bsfl %eax, %eax
+; X86-NOCMOV-NEXT:    bsfl %eax, %eax
 ; X86-NOCMOV-NEXT:    xorl %edx, %edx
 ; X86-NOCMOV-NEXT:    retl
 ;
@ -1008,8 +1008,8 @@ define i64 @cttz_i64_zero_test_knownneverzero(i64 %n) {
 ; X86-CMOV-NEXT:    movl {{[0-9]+}}(%esp), %ecx
 ; X86-CMOV-NEXT:    movl $-2147483648, %eax # imm = 0x80000000
 ; X86-CMOV-NEXT:    orl {{[0-9]+}}(%esp), %eax
-; X86-CMOV-NEXT:    rep bsfl %ecx, %edx
-; X86-CMOV-NEXT:    rep bsfl %eax, %eax
+; X86-CMOV-NEXT:    bsfl %ecx, %edx
+; X86-CMOV-NEXT:    bsfl %eax, %eax
 ; X86-CMOV-NEXT:    orl $32, %eax
 ; X86-CMOV-NEXT:    testl %ecx, %ecx
 ; X86-CMOV-NEXT:    cmovnel %edx, %eax
@ -1020,7 +1020,7 @@ define i64 @cttz_i64_zero_test_knownneverzero(i64 %n) {
 ; X64:       # %bb.0:
 ; X64-NEXT:    movabsq $-9223372036854775808, %rax # imm = 0x8000000000000000
 ; X64-NEXT:    orq %rdi, %rax
-; X64-NEXT:    rep bsfq %rax, %rax
+; X64-NEXT:    bsfq %rax, %rax
 ; X64-NEXT:    retq
 ;
 ; X86-CLZ-LABEL: cttz_i64_zero_test_knownneverzero:
@ -1121,55 +1121,3 @@ define i32 @PR47603_zext(i32 %a0, ptr %a1) {
  %sext = sext i8 %load to i32
  ret i32 %sext
 }
-
-define i32 @cttz_i32_osize(i32 %x) optsize {
-; X86-LABEL: cttz_i32_osize:
-; X86:       # %bb.0:
-; X86-NOT:     rep
-; X86-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    retl
-;
-; X64-LABEL: cttz_i32_osize:
-; X64:       # %bb.0:
-; X64-NOT:     rep
-; X64-NEXT:    bsfl %edi, %eax
-; X64-NEXT:    retq
-;
-; X86-CLZ-LABEL: cttz_i32_osize:
-; X86-CLZ:       # %bb.0:
-; X86-CLZ-NEXT:    tzcntl {{[0-9]+}}(%esp), %eax
-; X86-CLZ-NEXT:    retl
-;
-; X64-CLZ-LABEL: cttz_i32_osize:
-; X64-CLZ:       # %bb.0:
-; X64-CLZ-NEXT:    tzcntl %edi, %eax
-; X64-CLZ-NEXT:    retq
-  %tmp = call i32 @llvm.cttz.i32( i32 %x, i1 true )
-  ret i32 %tmp
-}
-
-define i32 @cttz_i32_msize(i32 %x) minsize {
-; X86-LABEL: cttz_i32_msize:
-; X86:       # %bb.0:
-; X86-NOT:     rep
-; X86-NEXT:    bsfl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    retl
-;
-; X64-LABEL: cttz_i32_msize:
-; X64:       # %bb.0:
-; X64-NOT:     rep
-; X64-NEXT:    bsfl %edi, %eax
-; X64-NEXT:    retq
-;
-; X86-CLZ-LABEL: cttz_i32_msize:
-; X86-CLZ:       # %bb.0:
-; X86-CLZ-NEXT:    tzcntl {{[0-9]+}}(%esp), %eax
-; X86-CLZ-NEXT:    retl
-;
-; X64-CLZ-LABEL: cttz_i32_msize:
-; X64-CLZ:       # %bb.0:
-; X64-CLZ-NEXT:    tzcntl %edi, %eax
-; X64-CLZ-NEXT:    retq
-  %tmp = call i32 @llvm.cttz.i32( i32 %x, i1 true )
-  ret i32 %tmp
-}
--- a/llvm/test/CodeGen/X86/dagcombine-select.ll
+++ b/llvm/test/CodeGen/X86/dagcombine-select.ll
@ -281,7 +281,7 @@ declare i64 @llvm.cttz.i64(i64, i1)
 define i64 @cttz_64_eq_select(i64 %v) nounwind {
 ; NOBMI-LABEL: cttz_64_eq_select:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfq %rdi, %rcx
+; NOBMI-NEXT:    bsfq %rdi, %rcx
 ; NOBMI-NEXT:    movq $-1, %rax
 ; NOBMI-NEXT:    cmovneq %rcx, %rax
 ; NOBMI-NEXT:    addq $6, %rax
@ -305,7 +305,7 @@ define i64 @cttz_64_eq_select(i64 %v) nounwind {
 define i64 @cttz_64_ne_select(i64 %v) nounwind {
 ; NOBMI-LABEL: cttz_64_ne_select:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfq %rdi, %rcx
+; NOBMI-NEXT:    bsfq %rdi, %rcx
 ; NOBMI-NEXT:    movq $-1, %rax
 ; NOBMI-NEXT:    cmovneq %rcx, %rax
 ; NOBMI-NEXT:    addq $6, %rax
@ -330,7 +330,7 @@ declare i32 @llvm.cttz.i32(i32, i1)
 define i32 @cttz_32_eq_select(i32 %v) nounwind {
 ; NOBMI-LABEL: cttz_32_eq_select:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfl %edi, %ecx
+; NOBMI-NEXT:    bsfl %edi, %ecx
 ; NOBMI-NEXT:    movl $-1, %eax
 ; NOBMI-NEXT:    cmovnel %ecx, %eax
 ; NOBMI-NEXT:    addl $6, %eax
@ -354,7 +354,7 @@ define i32 @cttz_32_eq_select(i32 %v) nounwind {
 define i32 @cttz_32_ne_select(i32 %v) nounwind {
 ; NOBMI-LABEL: cttz_32_ne_select:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfl %edi, %ecx
+; NOBMI-NEXT:    bsfl %edi, %ecx
 ; NOBMI-NEXT:    movl $-1, %eax
 ; NOBMI-NEXT:    cmovnel %ecx, %eax
 ; NOBMI-NEXT:    addl $6, %eax
@ -379,7 +379,7 @@ define i32 @cttz_32_ne_select(i32 %v) nounwind {
 define i32 @cttz_32_eq_select_ffs(i32 %v) nounwind {
 ; NOBMI-LABEL: cttz_32_eq_select_ffs:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfl %edi, %ecx
+; NOBMI-NEXT:    bsfl %edi, %ecx
 ; NOBMI-NEXT:    movl $-1, %eax
 ; NOBMI-NEXT:    cmovnel %ecx, %eax
 ; NOBMI-NEXT:    incl %eax
@ -403,7 +403,7 @@ define i32 @cttz_32_eq_select_ffs(i32 %v) nounwind {
 define i32 @cttz_32_ne_select_ffs(i32 %v) nounwind {
 ; NOBMI-LABEL: cttz_32_ne_select_ffs:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfl %edi, %ecx
+; NOBMI-NEXT:    bsfl %edi, %ecx
 ; NOBMI-NEXT:    movl $-1, %eax
 ; NOBMI-NEXT:    cmovnel %ecx, %eax
 ; NOBMI-NEXT:    incl %eax
@ -428,7 +428,7 @@ define i32 @cttz_32_ne_select_ffs(i32 %v) nounwind {
 define i32 @cttz_32_eq_select_ffs_m1(i32 %v) nounwind {
 ; NOBMI-LABEL: cttz_32_eq_select_ffs_m1:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfl %edi, %ecx
+; NOBMI-NEXT:    bsfl %edi, %ecx
 ; NOBMI-NEXT:    movl $-1, %eax
 ; NOBMI-NEXT:    cmovnel %ecx, %eax
 ; NOBMI-NEXT:    retq
@ -449,7 +449,7 @@ define i32 @cttz_32_eq_select_ffs_m1(i32 %v) nounwind {
 define i32 @cttz_32_ne_select_ffs_m1(i32 %v) nounwind {
 ; NOBMI-LABEL: cttz_32_ne_select_ffs_m1:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    rep bsfl %edi, %ecx
+; NOBMI-NEXT:    bsfl %edi, %ecx
 ; NOBMI-NEXT:    movl $-1, %eax
 ; NOBMI-NEXT:    cmovnel %ecx, %eax
 ; NOBMI-NEXT:    retq
--- a/llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll
+++ b/llvm/test/CodeGen/X86/peephole-na-phys-copy-folding.ll
@ -353,7 +353,6 @@ define i1 @asm_clobbering_flags(ptr %mem) nounwind {
 ; CHECK32-NEXT:    testl %edx, %edx
 ; CHECK32-NEXT:    setg %al
 ; CHECK32-NEXT:    #APP
-; CHECK32-NOT:     rep
 ; CHECK32-NEXT:    bsfl %edx, %edx
 ; CHECK32-NEXT:    #NO_APP
 ; CHECK32-NEXT:    movl %edx, (%ecx)
@ -365,7 +364,6 @@ define i1 @asm_clobbering_flags(ptr %mem) nounwind {
 ; CHECK64-NEXT:    testl %ecx, %ecx
 ; CHECK64-NEXT:    setg %al
 ; CHECK64-NEXT:    #APP
-; CHECK64-NOT:     rep
 ; CHECK64-NEXT:    bsfl %ecx, %ecx
 ; CHECK64-NEXT:    #NO_APP
 ; CHECK64-NEXT:    movl %ecx, (%rdi)
--- a/llvm/test/CodeGen/X86/stack-folding-x86_64.ll
+++ b/llvm/test/CodeGen/X86/stack-folding-x86_64.ll
@ -37,7 +37,7 @@ define i32 @stack_fold_bsf_i32(i32 %a0) {
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    rep bsfl {{[-0-9]+}}(%r{{[sb]}}p), %eax # 4-byte Folded Reload
+; CHECK-NEXT:    bsfl {{[-0-9]+}}(%r{{[sb]}}p), %eax # 4-byte Folded Reload
 ; CHECK-NEXT:    popq %rbx
 ; CHECK-NEXT:    .cfi_def_cfa_offset 48
 ; CHECK-NEXT:    popq %r12
@ -82,7 +82,7 @@ define i64 @stack_fold_bsf_i64(i64 %a0) {
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    rep bsfq {{[-0-9]+}}(%r{{[sb]}}p), %rax # 8-byte Folded Reload
+; CHECK-NEXT:    bsfq {{[-0-9]+}}(%r{{[sb]}}p), %rax # 8-byte Folded Reload
 ; CHECK-NEXT:    popq %rbx
 ; CHECK-NEXT:    .cfi_def_cfa_offset 48
 ; CHECK-NEXT:    popq %r12