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Fix PR tree-optimization/34046
- From: Eric Botcazou <ebotcazou at libertysurf dot fr>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 14 Nov 2007 20:08:32 +0100
- Subject: Fix PR tree-optimization/34046
This is another item in the series "negative edge probabilities out of integer
overflow", a regression present at -O3 on the mainline. If several incoming
edges of a basic block are to be threaded, update_bb_profile_for_threading is
invoked several times and rescales the edges probabilities each time; these
can quickly become very low and, at this point, quirks related to integer
division can seriously come into play.
This has already been accounted for in the scaling loop:
FOR_EACH_EDGE (c, ei, bb->succs)
{
c->probability = RDIV (c->probability * scale, 65536);
if (c->probability > REG_BR_PROB_BASE)
c->probability = REG_BR_PROB_BASE;
}
Theoritically, c->probability can never be greater than REG_BR_PROB_BASE but,
in practice, it can if c->probability was greater than the new base; this
latter case can theoritically never happen but, in practice, it also does for
the reasons explained above. Now, in the latter case, if the new base is
very small, c->probability * scale will overflow and the division yields a
negative result.
Fixed by avoiding the division in this case, tested on x86_64-suse-linux,
applied on the mainline as obvious.
2007-11-14 Eric Botcazou <ebotcazou@libertysurf.fr>
PR tree-optimization/34046
* cfg.c (update_bb_profile_for_threading): Avoid the division for the
scaling if the old probability is greater than the new base.
2007-11-14 Eric Botcazou <ebotcazou@libertysurf.fr>
* gcc.c-torture/compile/20071114-1.c: New test.
--
Eric Botcazou
Index: cfg.c
===================================================================
--- cfg.c (revision 130131)
+++ cfg.c (working copy)
@@ -990,9 +990,15 @@ update_bb_profile_for_threading (basic_b
FOR_EACH_EDGE (c, ei, bb->succs)
{
- c->probability = RDIV (c->probability * scale, 65536);
- if (c->probability > REG_BR_PROB_BASE)
+ /* Protect from overflow due to additional scaling. */
+ if (c->probability > prob)
c->probability = REG_BR_PROB_BASE;
+ else
+ {
+ c->probability = RDIV (c->probability * scale, 65536);
+ if (c->probability > REG_BR_PROB_BASE)
+ c->probability = REG_BR_PROB_BASE;
+ }
}
}
/* PR tree-optimization/34046 */
/* Origin: dcb <dcb314@hotmail.com> */
typedef unsigned char bool8;
typedef unsigned char uint8_t;
typedef unsigned short int uint16_t;
typedef unsigned int uint32_t;
typedef uint8_t uint8;
typedef uint16_t uint16;
typedef uint32_t uint32;
struct SIAPU
{
uint8 *PC;
uint8 *RAM;
uint8 Bit;
uint32 Address;
uint8 *WaitAddress1;
uint8 *WaitAddress2;
uint8 _Carry;
};
struct SAPU
{
bool8 ShowROM;
uint8 OutPorts [4];
uint8 ExtraRAM [64];
uint16 TimerTarget [3];
};
struct SAPU APU;
struct SIAPU IAPU;
void S9xSetAPUControl (uint8 byte);
void S9xSetAPUDSP (uint8 byte);
uint8 S9xGetAPUDSP ();
uint8 S9xAPUGetByte (uint32 Address)
{
Address &= 0xffff;
if (Address <= 0xff && Address >= 0xf0)
{
if (Address >= 0xf4 && Address <= 0xf7)
{
IAPU.WaitAddress2 = IAPU.WaitAddress1;
IAPU.WaitAddress1 = IAPU.PC;
return (IAPU.RAM [Address]);
}
else if (Address == 0xf3)
return (S9xGetAPUDSP ());
if (Address >= 0xfd)
{
IAPU.WaitAddress2 = IAPU.WaitAddress1;
IAPU.WaitAddress1 = IAPU.PC;
uint8 t = IAPU.RAM [Address];
IAPU.RAM [Address] = 0;
return (t);
}
return (IAPU.RAM [Address]);
}
else
return (IAPU.RAM [Address]);
}
void S9xAPUSetByte (uint8 byte, uint32 Address)
{
Address &= 0xffff;
if (Address <= 0xff && Address >= 0xf0)
{
if (Address == 0xf3)
S9xSetAPUDSP (byte);
else if (Address >= 0xf4 && Address <= 0xf7)
APU.OutPorts [Address - 0xf4] = byte;
else if (Address == 0xf1)
S9xSetAPUControl (byte);
else if (Address < 0xfd)
{
IAPU.RAM [Address] = byte;
if (Address >= 0xfa)
{
if (byte == 0)
APU.TimerTarget [Address - 0xfa] = 0x100;
else
APU.TimerTarget [Address - 0xfa] = byte;
}
}
}
else
{
if (Address < 0xffc0)
IAPU.RAM [Address] = byte;
else
{
APU.ExtraRAM [Address - 0xffc0] = byte;
if (!APU.ShowROM)
IAPU.RAM [Address] = byte;
}
}
}
void ApuCA ()
{
IAPU.Address = *(uint16 *) (IAPU.PC + 1);
IAPU.Bit = (uint8)(IAPU.Address >> 13);
if ((IAPU._Carry))
S9xAPUSetByte (S9xAPUGetByte (IAPU.Address) | (1 << IAPU.Bit), IAPU.Address);
else
S9xAPUSetByte (S9xAPUGetByte (IAPU.Address) & ~(1 << IAPU.Bit), IAPU.Address);
}