return;
}
- bool FromEFLAGS = SrcReg == X86::EFLAGS;
- bool ToEFLAGS = DestReg == X86::EFLAGS;
- int Reg = FromEFLAGS ? DestReg : SrcReg;
- bool is32 = X86::GR32RegClass.contains(Reg);
- bool is64 = X86::GR64RegClass.contains(Reg);
- if ((FromEFLAGS || ToEFLAGS) && (is32 || is64)) {
- // The flags need to be saved, but saving EFLAGS with PUSHF/POPF is
- // inefficient. Instead:
- // - Save the overflow flag OF into AL using SETO, and restore it using a
- // signed 8-bit addition of AL and INT8_MAX.
- // - Save/restore the bottom 8 EFLAGS bits (CF, PF, AF, ZF, SF) to/from AH
- // using LAHF/SAHF.
- // - When RAX/EAX is live and isn't the destination register, make sure it
- // isn't clobbered by PUSH/POP'ing it before and after saving/restoring
- // the flags.
- // This approach is ~2.25x faster than using PUSHF/POPF.
- //
- // This is still somewhat inefficient because we don't know which flags are
- // actually live inside EFLAGS. Were we able to do a single SETcc instead of
- // SETO+LAHF / ADDB+SAHF the code could be 1.02x faster.
- //
- // Notice that we have to adjust the stack if we don't want to clobber the
- // first frame index. See X86FrameLowering.cpp - clobbersTheStack.
-
- int Mov = is64 ? X86::MOV64rr : X86::MOV32rr;
- int Push = is64 ? X86::PUSH64r : X86::PUSH32r;
- int Pop = is64 ? X86::POP64r : X86::POP32r;
- int AX = is64 ? X86::RAX : X86::EAX;
-
- bool AXDead = (Reg == AX) ||
- (MachineBasicBlock::LQR_Dead ==
- MBB.computeRegisterLiveness(&getRegisterInfo(), AX, MI));
-
- if (!AXDead)
- BuildMI(MBB, MI, DL, get(Push)).addReg(AX, getKillRegState(true));
- if (FromEFLAGS) {
- BuildMI(MBB, MI, DL, get(X86::SETOr), X86::AL);
- BuildMI(MBB, MI, DL, get(X86::LAHF));
- BuildMI(MBB, MI, DL, get(Mov), Reg).addReg(AX);
+ // Moving EFLAGS to / from another register requires a push and a pop.
+ // Notice that we have to adjust the stack if we don't want to clobber the
+ // first frame index. See X86FrameLowering.cpp - clobbersTheStack.
+ if (SrcReg == X86::EFLAGS) {
+ if (X86::GR64RegClass.contains(DestReg)) {
+ BuildMI(MBB, MI, DL, get(X86::PUSHF64));
+ BuildMI(MBB, MI, DL, get(X86::POP64r), DestReg);
+ return;
}
- if (ToEFLAGS) {
- BuildMI(MBB, MI, DL, get(Mov), AX).addReg(Reg, getKillRegState(KillSrc));
- BuildMI(MBB, MI, DL, get(X86::ADD8ri), X86::AL)
- .addReg(X86::AL)
- .addImm(INT8_MAX);
- BuildMI(MBB, MI, DL, get(X86::SAHF));
+ if (X86::GR32RegClass.contains(DestReg)) {
+ BuildMI(MBB, MI, DL, get(X86::PUSHF32));
+ BuildMI(MBB, MI, DL, get(X86::POP32r), DestReg);
+ return;
+ }
+ }
+ if (DestReg == X86::EFLAGS) {
+ if (X86::GR64RegClass.contains(SrcReg)) {
+ BuildMI(MBB, MI, DL, get(X86::PUSH64r))
+ .addReg(SrcReg, getKillRegState(KillSrc));
+ BuildMI(MBB, MI, DL, get(X86::POPF64));
+ return;
+ }
+ if (X86::GR32RegClass.contains(SrcReg)) {
+ BuildMI(MBB, MI, DL, get(X86::PUSH32r))
+ .addReg(SrcReg, getKillRegState(KillSrc));
+ BuildMI(MBB, MI, DL, get(X86::POPF32));
+ return;
}
- if (!AXDead)
- BuildMI(MBB, MI, DL, get(Pop), AX);
- return;
}
DEBUG(dbgs() << "Cannot copy " << RI.getName(SrcReg)
-; RUN: llc -verify-machineinstrs -mtriple=i386-linux-gnu %s -o - | FileCheck %s -check-prefix=i386
-; RUN: llc -verify-machineinstrs -mtriple=i386-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s -check-prefix=i386f
-; RUN: llc -verify-machineinstrs -mtriple=x86_64-linux-gnu %s -o - | FileCheck %s -check-prefix=x8664
-; RUN: llc -verify-machineinstrs -mtriple=x86_64-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s -check-prefix=x8664
+; RUN: llc -verify-machineinstrs -mtriple=i386-linux-gnu %s -o - | FileCheck %s
+; RUN: llc -verify-machineinstrs -mtriple=i386-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s
+; RUN: llc -verify-machineinstrs -mtriple=x86_64-linux-gnu %s -o - | FileCheck %s
+; RUN: llc -verify-machineinstrs -mtriple=x86_64-linux-gnu -pre-RA-sched=fast %s -o - | FileCheck %s
-declare i32 @foo()
-declare i32 @bar(i64)
+declare i32 @bar()
define i64 @test_intervening_call(i64* %foo, i64 %bar, i64 %baz) {
-; i386-LABEL: test_intervening_call:
-; i386: cmpxchg8b
-; i386-NEXT: pushl %eax
-; i386-NEXT: seto %al
-; i386-NEXT: lahf
-; i386-NEXT: movl %eax, [[FLAGS:%.*]]
-; i386-NEXT: popl %eax
-; i386-NEXT: movl %edx, 4(%esp)
-; i386-NEXT: movl %eax, (%esp)
-; i386-NEXT: calll bar
-; i386-NEXT: movl [[FLAGS]], %eax
-; i386-NEXT: addb $127, %al
-; i386-NEXT: sahf
-; i386-NEXT: jne
-
-; i386f-LABEL: test_intervening_call:
-; i386f: cmpxchg8b
-; i386f-NEXT: movl %eax, (%esp)
-; i386f-NEXT: movl %edx, 4(%esp)
-; i386f-NEXT: seto %al
-; i386f-NEXT: lahf
-; i386f-NEXT: movl %eax, [[FLAGS:%.*]]
-; i386f-NEXT: calll bar
-; i386f-NEXT: movl [[FLAGS]], %eax
-; i386f-NEXT: addb $127, %al
-; i386f-NEXT: sahf
-; i386f-NEXT: jne
-
-; x8664-LABEL: test_intervening_call:
-; x8664: cmpxchgq
-; x8664: pushq %rax
-; x8664-NEXT: seto %al
-; x8664-NEXT: lahf
-; x8664-NEXT: movq %rax, [[FLAGS:%.*]]
-; x8664-NEXT: popq %rax
-; x8664-NEXT: movq %rax, %rdi
-; x8664-NEXT: callq bar
-; x8664-NEXT: movq [[FLAGS]], %rax
-; x8664-NEXT: addb $127, %al
-; x8664-NEXT: sahf
-; x8664-NEXT: jne
+; CHECK-LABEL: test_intervening_call:
+; CHECK: cmpxchg
+; CHECK: pushf[[LQ:[lq]]]
+; CHECK-NEXT: pop[[LQ]] [[FLAGS:%.*]]
+; CHECK-NEXT: call[[LQ]] bar
+
+; CHECK-NEXT: push[[LQ]] [[FLAGS]]
+; CHECK-NEXT: popf[[LQ]]
+; CHECK-NEXT: jne
%cx = cmpxchg i64* %foo, i64 %bar, i64 %baz seq_cst seq_cst
- %v = extractvalue { i64, i1 } %cx, 0
%p = extractvalue { i64, i1 } %cx, 1
- call i32 @bar(i64 %v)
+ call i32 @bar()
br i1 %p, label %t, label %f
t:
; Interesting in producing a clobber without any function calls.
define i32 @test_control_flow(i32* %p, i32 %i, i32 %j) {
-; i386-LABEL: test_control_flow:
-; i386: cmpxchg
-; i386-NEXT: jne
-
-; i386f-LABEL: test_control_flow:
-; i386f: cmpxchg
-; i386f-NEXT: jne
-
-; x8664-LABEL: test_control_flow:
-; x8664: cmpxchg
-; x8664-NEXT: jne
+; CHECK-LABEL: test_control_flow:
+; CHECK: cmpxchg
+; CHECK-NEXT: jne
entry:
%cmp = icmp sgt i32 %i, %j
br i1 %cmp, label %loop_start, label %cond.end
; This one is an interesting case because CMOV doesn't have a chain
; operand. Naive attempts to limit cmpxchg EFLAGS use are likely to fail here.
define i32 @test_feed_cmov(i32* %addr, i32 %desired, i32 %new) {
-; i386-LABEL: test_feed_cmov:
-; i386: cmpxchgl
-; i386-NEXT: seto %al
-; i386-NEXT: lahf
-; i386-NEXT: movl %eax, [[FLAGS:%.*]]
-; i386-NEXT: calll foo
-; i386-NEXT: pushl %eax
-; i386-NEXT: movl [[FLAGS]], %eax
-; i386-NEXT: addb $127, %al
-; i386-NEXT: sahf
-; i386-NEXT: popl %eax
-
-; i386f-LABEL: test_feed_cmov:
-; i386f: cmpxchgl
-; i386f-NEXT: seto %al
-; i386f-NEXT: lahf
-; i386f-NEXT: movl %eax, [[FLAGS:%.*]]
-; i386f-NEXT: calll foo
-; i386f-NEXT: pushl %eax
-; i386f-NEXT: movl [[FLAGS]], %eax
-; i386f-NEXT: addb $127, %al
-; i386f-NEXT: sahf
-; i386f-NEXT: popl %eax
-
-; x8664-LABEL: test_feed_cmov:
-; x8664: cmpxchgl
-; x8664: seto %al
-; x8664-NEXT: lahf
-; x8664-NEXT: movq %rax, [[FLAGS:%.*]]
-; x8664-NEXT: callq foo
-; x8664-NEXT: pushq %rax
-; x8664-NEXT: movq [[FLAGS]], %rax
-; x8664-NEXT: addb $127, %al
-; x8664-NEXT: sahf
-; x8664-NEXT: popq %rax
+; CHECK-LABEL: test_feed_cmov:
+
+; CHECK: cmpxchg
+; CHECK: pushf[[LQ:[lq]]]
+; CHECK-NEXT: pop[[LQ]] [[FLAGS:%.*]]
+
+; CHECK-NEXT: call[[LQ]] bar
+; CHECK-NEXT: push[[LQ]] [[FLAGS]]
+; CHECK-NEXT: popf[[LQ]]
%res = cmpxchg i32* %addr, i32 %desired, i32 %new seq_cst seq_cst
%success = extractvalue { i32, i1 } %res, 1
- %rhs = call i32 @foo()
+ %rhs = call i32 @bar()
%ret = select i1 %success, i32 %new, i32 %rhs
ret i32 %ret