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Support nocheck prefix #35491

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Support nocheck prefix #35491

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18ee73c
Provide initial support for no. (no check) prefix
john-h-k Apr 26, 2020
6afefad
Remove PREFIX_NOCHECK_FLAGS enum and just have them as 3 seperate flags
john-h-k Apr 26, 2020
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2 changes: 1 addition & 1 deletion src/coreclr/src/inc/opcode.def
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Original file line number Diff line number Diff line change
Expand Up @@ -317,7 +317,7 @@ OPDEF(CEE_INITOBJ, "initobj", PopI, Pu
OPDEF(CEE_CONSTRAINED, "constrained.", Pop0, Push0, InlineType, IPrefix, 2, 0xFE, 0x16, META)
OPDEF(CEE_CPBLK, "cpblk", PopI+PopI+PopI, Push0, InlineNone, IPrimitive, 2, 0xFE, 0x17, NEXT)
OPDEF(CEE_INITBLK, "initblk", PopI+PopI+PopI, Push0, InlineNone, IPrimitive, 2, 0xFE, 0x18, NEXT)
OPDEF(CEE_UNUSED69, "unused", Pop0, Push0, InlineNone, IPrimitive, 2, 0xFE, 0x19, NEXT)
OPDEF(CEE_NOCHECK, "no.", Pop0, Push0, ShortInlineI, IPrefix, 2, 0xFE, 0x19, META)
OPDEF(CEE_RETHROW, "rethrow", Pop0, Push0, InlineNone, IObjModel, 2, 0xFE, 0x1A, THROW)
OPDEF(CEE_UNUSED51, "unused", Pop0, Push0, InlineNone, IPrimitive, 2, 0xFE, 0x1B, NEXT)
OPDEF(CEE_SIZEOF, "sizeof", Pop0, PushI, InlineType, IPrimitive, 2, 0xFE, 0x1C, NEXT)
Expand Down
2 changes: 2 additions & 0 deletions src/coreclr/src/jit/flowgraph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4702,6 +4702,7 @@ void Compiler::fgFindJumpTargets(const BYTE* codeAddr, IL_OFFSET codeSize, Fixed
case CEE_CONSTRAINED:
case CEE_READONLY:
case CEE_VOLATILE:
case CEE_NOCHECK:
case CEE_TAILCALL:
{
if (codeAddr >= codeEndp)
Expand Down Expand Up @@ -5607,6 +5608,7 @@ unsigned Compiler::fgMakeBasicBlocks(const BYTE* codeAddr, IL_OFFSET codeSize, F
case CEE_CONSTRAINED:
case CEE_VOLATILE:
case CEE_UNALIGNED:
case CEE_NOCHECK:
// fgFindJumpTargets should have ruled out this possibility
// (i.e. a prefix opcodes as last intruction in a block)
noway_assert(codeAddr < codeEndp);
Expand Down
82 changes: 75 additions & 7 deletions src/coreclr/src/jit/importer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7199,14 +7199,19 @@ bool Compiler::impTailCallRetTypeCompatible(var_types callerRetType,
// For prefixFlags
enum
{
PREFIX_TAILCALL_EXPLICIT = 0x00000001, // call has "tail" IL prefix
PREFIX_TAILCALL_EXPLICIT = 0x000000001, // call has "tail" IL prefix
PREFIX_TAILCALL_IMPLICIT =
0x00000010, // call is treated as having "tail" prefix even though there is no "tail" IL prefix
PREFIX_TAILCALL = (PREFIX_TAILCALL_EXPLICIT | PREFIX_TAILCALL_IMPLICIT),
PREFIX_VOLATILE = 0x00000100,
PREFIX_UNALIGNED = 0x00001000,
PREFIX_CONSTRAINED = 0x00010000,
PREFIX_READONLY = 0x00100000
0x000000002, // call is treated as having "tail" prefix even though there is no "tail" IL prefix
PREFIX_TAILCALL = (PREFIX_TAILCALL_EXPLICIT | PREFIX_TAILCALL_IMPLICIT),
PREFIX_VOLATILE = 0x000000004,
PREFIX_UNALIGNED = 0x000000008,
PREFIX_CONSTRAINED = 0x000000010,
PREFIX_READONLY = 0x000000020,
// DO NOT CHANGE THESE VALUES - impImportBlockCode (at case CEE_NOCHECK) relies on these being 6 bits left of the IL no. prefix flags
PREFIX_NO_TYPECHECK = 0x000000040,
PREFIX_NO_RANGECHECK = 0x000000080,
PREFIX_NO_NULLCHECK = 0x000000100,
PREFIX_NO_TYPERANGENULLCHECK = (PREFIX_NO_TYPECHECK | PREFIX_NO_RANGECHECK | PREFIX_NO_NULLCHECK)
};

/********************************************************************************
Expand Down Expand Up @@ -10005,6 +10010,7 @@ static OPCODE impGetNonPrefixOpcode(const BYTE* codeAddr, const BYTE* codeEndp)
case CEE_TAILCALL:
case CEE_CONSTRAINED:
case CEE_READONLY:
case CEE_NOCHECK:
break;
default:
return opcode;
Expand Down Expand Up @@ -10035,6 +10041,38 @@ static void impValidateMemoryAccessOpcode(const BYTE* codeAddr, const BYTE* code
}
}

/*****************************************************************************/
// Checks whether the opcode is a valid opcode for no. (check elision) prefix
static void impValidateCheckElisionOpcode(const BYTE* codeAddr, const BYTE* codeEndp, int flags)
{
OPCODE opcode = impGetNonPrefixOpcode(codeAddr, codeEndp);

if ((flags & PREFIX_NO_TYPECHECK) != 0)
{
if (!(opcode == CEE_CASTCLASS || opcode == CEE_UNBOX || opcode == CEE_LDELEMA
|| (opcode >= CEE_STELEM_I && opcode <= CEE_STELEM_REF) || opcode == CEE_STELEM))
{
BADCODE("Invalid opcode for no. prefix with typecheck flag");
}
}
if ((flags & PREFIX_NO_RANGECHECK) != 0)
{
// Covers LDELEMA, LDELEM_*, and STELEM_*
if (!(opcode >= CEE_LDELEMA && opcode <= CEE_STELEM))
{
BADCODE("Invalid opcode for no. prefix with rangecheck flag");
}
}
if ((flags & PREFIX_NO_NULLCHECK) != 0)
{
if (!(opcode == CEE_LDFLD || opcode == CEE_STFLD || opcode == CEE_CALLVIRT || opcode == CEE_LDVIRTFTN
|| (opcode >= CEE_LDELEMA && opcode <= CEE_STELEM)))
{
BADCODE("Invalid opcode for no. prefix with nullcheck flag");
}
}
}

/*****************************************************************************/

#ifdef DEBUG
Expand Down Expand Up @@ -13539,6 +13577,36 @@ void Compiler::impImportBlockCode(BasicBlock* block)
assert(sz == 0);
goto PREFIX;

case CEE_NOCHECK:
assert(sz == 1);
JITDUMP(" no.");
Verify(!(prefixFlags & PREFIX_NO_TYPERANGENULLCHECK), "Multiple no. prefixes");

{
int flags = getU1LittleEndian(codeAddr);

JITDUMP(" %u", flags);

++codeAddr;

// PREFIX_NO_TYPECHECK = 0x000000040 which is 0x1 (the value of typecheck flag) << 6
// The 2 subsequent flags are just left shift of 1, the same as the nullcheck/rangecheck IL flags, so we just have to
// left shift by 6 to transform
flags <<= 6;
if ((flags & (~PREFIX_NO_TYPERANGENULLCHECK)) != 0)
{
BADCODE("no. followed by invalid flags");
}

impValidateCheckElisionOpcode(codeAddr, codeEndp, flags);



prefixFlags |= flags;
}

goto PREFIX;

case CEE_TAILCALL:
JITDUMP(" tail.");

Expand Down