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Fix large stack alignment codegen for ARM and Thumb2 targets 

This partially fixes PR13007 (ARM CodeGen fails with large stack
alignment): for ARM and Thumb2 targets, but not for Thumb1, as it
seems stack alignment for Thumb1 targets hasn't been supported at
all.

Producing an aligned stack pointer is done by zero-ing out the lower
bits of the stack pointer. The BIC instruction was used for this.
However, the immediate field of the BIC instruction only allows to
encode an immediate that can zero out up to a maximum of the 8 lower
bits. When a larger alignment is requested, a BIC instruction cannot
be used; llvm was silently producing incorrect code in this case.

This commit fixes code generation for large stack aligments by
using the BFC instruction instead, when the BFC instruction is
available.  When not, it uses 2 instructions: a right shift,
followed by a left shift to zero out the lower bits.

The lowering of ARM::Int_eh_sjlj_dispatchsetup still has code
that unconditionally uses BIC to realign the stack pointer, so it
very likely has the same problem. However, I wasn't able to
produce a test case for that. This commit adds an assert so that
the compiler will fail the assert instead of silently generating
wrong code if this is ever reached.

llvm-svn: 225446
This commit is contained in:
Kristof Beyls 2015-01-08 15:09:14 +00:00
parent 654d669e56
commit 933de7aa06
9 changed files with 263 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
View File

@ -887,6 +887,9 @@ bool ARMExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
unsigned MaxAlign = MFI->getMaxAlignment();
assert (!AFI->isThumb1OnlyFunction());
// Emit bic r6, r6, MaxAlign
assert(MaxAlign <= 256 && "The BIC instruction cannot encode "
"immediates larger than 256 with all lower "
"bits set.");
unsigned bicOpc = AFI->isThumbFunction() ?
ARM::t2BICri : ARM::BICri;
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, MI.getDebugLoc(),

93
llvm/lib/Target/ARM/ARMFrameLowering.cpp
View File

@ -211,6 +211,68 @@ struct StackAdjustingInsts {
};
}
/// Emit an instruction sequence that will align the address in
/// register Reg by zero-ing out the lower bits. For versions of the
/// architecture that support Neon, this must be done in a single
/// instruction, since skipAlignedDPRCS2Spills assumes it is done in a
/// single instruction. That function only gets called when optimizing
/// spilling of D registers on a core with the Neon instruction set
/// present.
static void emitAligningInstructions(MachineFunction &MF, ARMFunctionInfo *AFI,
const TargetInstrInfo &TII,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
DebugLoc DL, const unsigned Reg,
const unsigned Alignment,
const bool MustBeSingleInstruction) {
const ARMSubtarget &AST = MF.getTarget().getSubtarget<ARMSubtarget>();
const bool CanUseBFC = AST.hasV6T2Ops() || AST.hasV7Ops();
const unsigned AlignMask = Alignment - 1;
const unsigned NrBitsToZero = countTrailingZeros(Alignment);
assert(!AFI->isThumb1OnlyFunction() && "Thumb1 not supported");
if (!AFI->isThumbFunction()) {
// if the BFC instruction is available, use that to zero the lower
// bits:
// bfc Reg, #0, log2(Alignment)
// otherwise use BIC, if the mask to zero the required number of bits
// can be encoded in the bic immediate field
// bic Reg, Reg, Alignment-1
// otherwise, emit
// lsr Reg, Reg, log2(Alignment)
// lsl Reg, Reg, log2(Alignment)
if (CanUseBFC) {
AddDefaultPred(BuildMI(MBB, MBBI, DL, TII.get(ARM::BFC), Reg)
.addReg(Reg, RegState::Kill)
.addImm(~AlignMask));
} else if (AlignMask <= 255) {
AddDefaultCC(
AddDefaultPred(BuildMI(MBB, MBBI, DL, TII.get(ARM::BICri), Reg)
.addReg(Reg, RegState::Kill)
.addImm(AlignMask)));
} else {
assert(!MustBeSingleInstruction &&
"Shouldn't call emitAligningInstructions demanding a single "
"instruction to be emitted for large stack alignment for a target "
"without BFC.");
AddDefaultCC(AddDefaultPred(
BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg)
.addReg(Reg, RegState::Kill)
.addImm(ARM_AM::getSORegOpc(ARM_AM::lsr, NrBitsToZero))));
AddDefaultCC(AddDefaultPred(
BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg)
.addReg(Reg, RegState::Kill)
.addImm(ARM_AM::getSORegOpc(ARM_AM::lsl, NrBitsToZero))));
}
} else {
// Since this is only reached for Thumb-2 targets, the BFC instruction
// should always be available.
assert(CanUseBFC);
AddDefaultPred(BuildMI(MBB, MBBI, DL, TII.get(ARM::t2BFC), Reg)
.addReg(Reg, RegState::Kill)
.addImm(~AlignMask));
}
}
void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front();
MachineBasicBlock::iterator MBBI = MBB.begin();
@ -570,24 +632,20 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
unsigned MaxAlign = MFI->getMaxAlignment();
assert(!AFI->isThumb1OnlyFunction());
if (!AFI->isThumbFunction()) {
// Emit bic sp, sp, MaxAlign
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
TII.get(ARM::BICri), ARM::SP)
.addReg(ARM::SP, RegState::Kill)
.addImm(MaxAlign-1)));
emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::SP, MaxAlign,
false);
} else {
// We cannot use sp as source/dest register here, thus we're emitting the
// following sequence:
// We cannot use sp as source/dest register here, thus we're using r4 to
// perform the calculations. We're emitting the following sequence:
// mov r4, sp
// bic r4, r4, MaxAlign
// -- use emitAligningInstructions to produce best sequence to zero
// -- out lower bits in r4
// mov sp, r4
// FIXME: It will be better just to find spare register here.
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4)
.addReg(ARM::SP, RegState::Kill));
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
TII.get(ARM::t2BICri), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(MaxAlign-1)));
emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::R4, MaxAlign,
false);
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(ARM::R4, RegState::Kill));
}
@ -1087,12 +1145,13 @@ static void emitAlignedDPRCS2Spills(MachineBasicBlock &MBB,
.addReg(ARM::SP)
.addImm(8 * NumAlignedDPRCS2Regs)));
// bic r4, r4, #align-1
Opc = isThumb ? ARM::t2BICri : ARM::BICri;
unsigned MaxAlign = MF.getFrameInfo()->getMaxAlignment();
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(MaxAlign - 1)));
// We must set parameter MustBeSingleInstruction to true, since
// skipAlignedDPRCS2Spills expects exactly 3 instructions to perform
// stack alignment. Luckily, this can always be done since all ARM
// architecture versions that support Neon also support the BFC
// instruction.
emitAligningInstructions(MF, AFI, TII, MBB, MI, DL, ARM::R4, MaxAlign, true);
// mov sp, r4
// The stack pointer must be adjusted before spilling anything, otherwise

2
llvm/test/CodeGen/ARM/alloc-no-stack-realign.ll
View File

@ -41,7 +41,7 @@ entry:
define void @test2(<16 x float>* noalias sret %agg.result) nounwind ssp {
entry:
; REALIGN-LABEL: test2
; REALIGN: bic sp, sp, #63
; REALIGN: bfc sp, #0, #6
; REALIGN: mov r[[R2:[0-9]+]], r[[R1:[0-9]+]]
; REALIGN: vld1.32 {{{d[0-9]+, d[0-9]+}}}, [r[[R2]]:128]!
; REALIGN: vld1.64 {{{d[0-9]+, d[0-9]+}}}, [r[[R2]]:128]

2
llvm/test/CodeGen/ARM/fold-stack-adjust.ll
View File

@ -71,7 +71,7 @@ define void @check_vfp_fold() minsize {
; CHECK-IOS-LABEL: check_vfp_fold:
; CHECK-IOS: push {r0, r1, r2, r3, r4, r7, lr}
; CHECK-IOS: sub.w r4, sp, #16
; CHECK-IOS: bic r4, r4, #15
; CHECK-IOS: bfc r4, #0, #4
; CHECK-IOS: mov sp, r4
; CHECK-IOS: vst1.64 {d8, d9}, [r4:128]
; ...

14
llvm/test/CodeGen/ARM/interrupt-attr.ll
View File

@ -15,7 +15,7 @@ define arm_aapcscc void @irq_fn() alignstack(8) "interrupt"="IRQ" {
; CHECK-A: push {r0, r1, r2, r3, r10, r11, r12, lr}
; CHECK-A: add r11, sp, #20
; CHECK-A-NOT: sub sp, sp, #{{[0-9]+}}
; CHECK-A: bic sp, sp, #7
; CHECK-A: bfc sp, #0, #3
; CHECK-A: bl bar
; CHECK-A: sub sp, r11, #20
; CHECK-A: pop {r0, r1, r2, r3, r10, r11, r12, lr}
@ -25,7 +25,7 @@ define arm_aapcscc void @irq_fn() alignstack(8) "interrupt"="IRQ" {
; CHECK-A-THUMB: push.w {r0, r1, r2, r3, r4, r7, r12, lr}
; CHECK-A-THUMB: add r7, sp, #20
; CHECK-A-THUMB: mov r4, sp
; CHECK-A-THUMB: bic r4, r4, #7
; CHECK-A-THUMB: bfc r4, #0, #3
; CHECK-A-THUMB: bl bar
; CHECK-A-THUMB: sub.w r4, r7, #20
; CHECK-A-THUMB: mov sp, r4
@ -38,7 +38,7 @@ define arm_aapcscc void @irq_fn() alignstack(8) "interrupt"="IRQ" {
; CHECK-M: push.w {r4, r10, r11, lr}
; CHECK-M: add.w r11, sp, #8
; CHECK-M: mov r4, sp
; CHECK-M: bic r4, r4, #7
; CHECK-M: bfc r4, #0, #3
; CHECK-M: mov sp, r4
; CHECK-M: bl _bar
; CHECK-M: sub.w r4, r11, #8
@ -56,7 +56,7 @@ define arm_aapcscc void @fiq_fn() alignstack(8) "interrupt"="FIQ" {
; 32 to get past r0, r1, ..., r7
; CHECK-A: add r11, sp, #32
; CHECK-A: sub sp, sp, #{{[0-9]+}}
; CHECK-A: bic sp, sp, #7
; CHECK-A: bfc sp, #0, #3
; [...]
; 32 must match above
; CHECK-A: sub sp, r11, #32
@ -75,7 +75,7 @@ define arm_aapcscc void @swi_fn() alignstack(8) "interrupt"="SWI" {
; CHECK-A: push {r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, lr}
; CHECK-A: add r11, sp, #44
; CHECK-A: sub sp, sp, #{{[0-9]+}}
; CHECK-A: bic sp, sp, #7
; CHECK-A: bfc sp, #0, #3
; [...]
; CHECK-A: sub sp, r11, #44
; CHECK-A: pop {r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, lr}
@ -91,7 +91,7 @@ define arm_aapcscc void @undef_fn() alignstack(8) "interrupt"="UNDEF" {
; CHECK-A: push {r0, r1, r2, r3, r10, r11, r12, lr}
; CHECK-A: add r11, sp, #20
; CHECK-A-NOT: sub sp, sp, #{{[0-9]+}}
; CHECK-A: bic sp, sp, #7
; CHECK-A: bfc sp, #0, #3
; [...]
; CHECK-A: sub sp, r11, #20
; CHECK-A: pop {r0, r1, r2, r3, r10, r11, r12, lr}
@ -106,7 +106,7 @@ define arm_aapcscc void @abort_fn() alignstack(8) "interrupt"="ABORT" {
; CHECK-A: push {r0, r1, r2, r3, r10, r11, r12, lr}
; CHECK-A: add r11, sp, #20
; CHECK-A-NOT: sub sp, sp, #{{[0-9]+}}
; CHECK-A: bic sp, sp, #7
; CHECK-A: bfc sp, #0, #3
; [...]
; CHECK-A: sub sp, r11, #20
; CHECK-A: pop {r0, r1, r2, r3, r10, r11, r12, lr}

2
llvm/test/CodeGen/ARM/spill-q.ll
View File

@ -11,7 +11,7 @@ declare <4 x float> @llvm.arm.neon.vld1.v4f32(i8*, i32) nounwind readonly
define void @aaa(%quuz* %this, i8* %block) {
; CHECK-LABEL: aaa:
; CHECK: bic {{.*}}, #15
; CHECK: bfc {{.*}}, #0, #4
; CHECK: vst1.64 {{.*}}sp:128
; CHECK: vld1.64 {{.*}}sp:128
entry:

164
llvm/test/CodeGen/ARM/stack-alignment.ll Normal file
View File

@ -0,0 +1,164 @@
; RUN: llc -verify-machineinstrs < %s -mtriple=armv4t | FileCheck %s -check-prefix=CHECK-v4A32
; RUN: llc -verify-machineinstrs < %s -mtriple=armv7a | FileCheck %s -check-prefix=CHECK-v7A32
; RUN: llc -verify-machineinstrs < %s -mtriple=thumbv7a | FileCheck %s -check-prefix=CHECK-THUMB2
; FIXME: There are no tests for Thumb1 since dynamic stack alignment is not supported for
; Thumb1.
define i32 @f_bic_can_be_used_align() nounwind {
entry:
; CHECK-LABEL: f_bic_can_be_used_align:
; CHECK-v7A32: bfc sp, #0, #8
; CHECK-v4A32: bic sp, sp, #255
; CHECK-THUMB2: mov r4, sp
; CHECK-THUMB2-NEXT: bfc r4, #0, #8
; CHECK-THUMB2-NEXT: mov sp, r4
%x = alloca i32, align 256
store volatile i32 0, i32* %x, align 256
ret i32 0
}
define i32 @f_too_large_for_bic_align() nounwind {
entry:
; CHECK-LABEL: f_too_large_for_bic_align:
; CHECK-v7A32: bfc sp, #0, #9
; CHECK-v4A32: lsr sp, sp, #9
; CHECK-v4A32: lsl sp, sp, #9
; CHECK-THUMB2: mov r4, sp
; CHECK-THUMB2-NEXT: bfc r4, #0, #9
; CHECK-THUMB2-NEXT: mov sp, r4
%x = alloca i32, align 512
store volatile i32 0, i32* %x, align 512
ret i32 0
}
define i8* @f_alignedDPRCS2Spills(double* %d) #0 {
entry:
; CHECK-LABEL: f_too_large_for_bic_align:
; CHECK-v7A32: bfc sp, #0, #12
; CHECK-v4A32: lsr sp, sp, #12
; CHECK-v4A32: lsl sp, sp, #12
; CHECK-THUMB2: bfc r4, #0, #12
; CHECK-THUMB2-NEXT: mov sp, r4
%a = alloca i8, align 4096
%0 = load double* %d, align 4
%arrayidx1 = getelementptr inbounds double* %d, i32 1
%1 = load double* %arrayidx1, align 4
%arrayidx2 = getelementptr inbounds double* %d, i32 2
%2 = load double* %arrayidx2, align 4
%arrayidx3 = getelementptr inbounds double* %d, i32 3
%3 = load double* %arrayidx3, align 4
%arrayidx4 = getelementptr inbounds double* %d, i32 4
%4 = load double* %arrayidx4, align 4
%arrayidx5 = getelementptr inbounds double* %d, i32 5
%5 = load double* %arrayidx5, align 4
%arrayidx6 = getelementptr inbounds double* %d, i32 6
%6 = load double* %arrayidx6, align 4
%arrayidx7 = getelementptr inbounds double* %d, i32 7
%7 = load double* %arrayidx7, align 4
%arrayidx8 = getelementptr inbounds double* %d, i32 8
%8 = load double* %arrayidx8, align 4
%arrayidx9 = getelementptr inbounds double* %d, i32 9
%9 = load double* %arrayidx9, align 4
%arrayidx10 = getelementptr inbounds double* %d, i32 10
%10 = load double* %arrayidx10, align 4
%arrayidx11 = getelementptr inbounds double* %d, i32 11
%11 = load double* %arrayidx11, align 4
%arrayidx12 = getelementptr inbounds double* %d, i32 12
%12 = load double* %arrayidx12, align 4
%arrayidx13 = getelementptr inbounds double* %d, i32 13
%13 = load double* %arrayidx13, align 4
%arrayidx14 = getelementptr inbounds double* %d, i32 14
%14 = load double* %arrayidx14, align 4
%arrayidx15 = getelementptr inbounds double* %d, i32 15
%15 = load double* %arrayidx15, align 4
%arrayidx16 = getelementptr inbounds double* %d, i32 16
%16 = load double* %arrayidx16, align 4
%arrayidx17 = getelementptr inbounds double* %d, i32 17
%17 = load double* %arrayidx17, align 4
%arrayidx18 = getelementptr inbounds double* %d, i32 18
%18 = load double* %arrayidx18, align 4
%arrayidx19 = getelementptr inbounds double* %d, i32 19
%19 = load double* %arrayidx19, align 4
%arrayidx20 = getelementptr inbounds double* %d, i32 20
%20 = load double* %arrayidx20, align 4
%arrayidx21 = getelementptr inbounds double* %d, i32 21
%21 = load double* %arrayidx21, align 4
%arrayidx22 = getelementptr inbounds double* %d, i32 22
%22 = load double* %arrayidx22, align 4
%arrayidx23 = getelementptr inbounds double* %d, i32 23
%23 = load double* %arrayidx23, align 4
%arrayidx24 = getelementptr inbounds double* %d, i32 24
%24 = load double* %arrayidx24, align 4
%arrayidx25 = getelementptr inbounds double* %d, i32 25
%25 = load double* %arrayidx25, align 4
%arrayidx26 = getelementptr inbounds double* %d, i32 26
%26 = load double* %arrayidx26, align 4
%arrayidx27 = getelementptr inbounds double* %d, i32 27
%27 = load double* %arrayidx27, align 4
%arrayidx28 = getelementptr inbounds double* %d, i32 28
%28 = load double* %arrayidx28, align 4
%arrayidx29 = getelementptr inbounds double* %d, i32 29
%29 = load double* %arrayidx29, align 4
%div = fdiv double %29, %28
%div30 = fdiv double %div, %27
%div31 = fdiv double %div30, %26
%div32 = fdiv double %div31, %25
%div33 = fdiv double %div32, %24
%div34 = fdiv double %div33, %23
%div35 = fdiv double %div34, %22
%div36 = fdiv double %div35, %21
%div37 = fdiv double %div36, %20
%div38 = fdiv double %div37, %19
%div39 = fdiv double %div38, %18
%div40 = fdiv double %div39, %17
%div41 = fdiv double %div40, %16
%div42 = fdiv double %div41, %15
%div43 = fdiv double %div42, %14
%div44 = fdiv double %div43, %13
%div45 = fdiv double %div44, %12
%div46 = fdiv double %div45, %11
%div47 = fdiv double %div46, %10
%div48 = fdiv double %div47, %9
%div49 = fdiv double %div48, %8
%div50 = fdiv double %div49, %7
%div51 = fdiv double %div50, %6
%div52 = fdiv double %div51, %5
%div53 = fdiv double %div52, %4
%div54 = fdiv double %div53, %3
%div55 = fdiv double %div54, %2
%div56 = fdiv double %div55, %1
%div57 = fdiv double %div56, %0
%div58 = fdiv double %0, %1
%div59 = fdiv double %div58, %2
%div60 = fdiv double %div59, %3
%div61 = fdiv double %div60, %4
%div62 = fdiv double %div61, %5
%div63 = fdiv double %div62, %6
%div64 = fdiv double %div63, %7
%div65 = fdiv double %div64, %8
%div66 = fdiv double %div65, %9
%div67 = fdiv double %div66, %10
%div68 = fdiv double %div67, %11
%div69 = fdiv double %div68, %12
%div70 = fdiv double %div69, %13
%div71 = fdiv double %div70, %14
%div72 = fdiv double %div71, %15
%div73 = fdiv double %div72, %16
%div74 = fdiv double %div73, %17
%div75 = fdiv double %div74, %18
%div76 = fdiv double %div75, %19
%div77 = fdiv double %div76, %20
%div78 = fdiv double %div77, %21
%div79 = fdiv double %div78, %22
%div80 = fdiv double %div79, %23
%div81 = fdiv double %div80, %24
%div82 = fdiv double %div81, %25
%div83 = fdiv double %div82, %26
%div84 = fdiv double %div83, %27
%div85 = fdiv double %div84, %28
%div86 = fdiv double %div85, %29
%mul = fmul double %div57, %div86
%conv = fptosi double %mul to i32
%add.ptr = getelementptr inbounds i8* %a, i32 %conv
ret i8* %add.ptr
}

8
llvm/test/CodeGen/Thumb2/aligned-spill.ll
View File

@ -9,7 +9,7 @@ target triple = "thumbv7-apple-ios"
;
; The caller-saved r4 is used as a scratch register for stack realignment.
; CHECK: push {r4, r7, lr}
; CHECK: bic r4, r4, #7
; CHECK: bfc r4, #0, #3
; CHECK: mov sp, r4
define void @f(double* nocapture %p) nounwind ssp {
entry:
@ -23,7 +23,7 @@ entry:
; NEON: f
; NEON: push {r4, r7, lr}
; NEON: sub.w r4, sp, #64
; NEON: bic r4, r4, #15
; NEON: bfc r4, #0, #4
; Stack pointer must be updated before the spills.
; NEON: mov sp, r4
; NEON: vst1.64 {d8, d9, d10, d11}, [r4:128]!
@ -54,7 +54,7 @@ entry:
; NEON: f7
; NEON: push {r4, r7, lr}
; NEON: sub.w r4, sp, #56
; NEON: bic r4, r4, #15
; NEON: bfc r4, #0, #4
; Stack pointer must be updated before the spills.
; NEON: mov sp, r4
; NEON: vst1.64 {d8, d9, d10, d11}, [r4:128]!
@ -81,7 +81,7 @@ entry:
; NEON: push {r4, r7, lr}
; NEON: vpush {d12, d13, d14, d15}
; NEON: sub.w r4, sp, #24
; NEON: bic r4, r4, #15
; NEON: bfc r4, #0, #4
; Stack pointer must be updated before the spills.
; NEON: mov sp, r4
; NEON: vst1.64 {d8, d9}, [r4:128]

2
llvm/test/CodeGen/Thumb2/thumb2-spill-q.ll
View File

@ -11,7 +11,7 @@ declare <4 x float> @llvm.arm.neon.vld1.v4f32(i8*, i32) nounwind readonly
define void @aaa(%quuz* %this, i8* %block) {
; CHECK-LABEL: aaa:
; CHECK: bic r4, r4, #15
; CHECK: bfc r4, #0, #4
; CHECK: vst1.64 {{.*}}[{{.*}}:128]
; CHECK: vld1.64 {{.*}}[{{.*}}:128]
entry: