Commit fea3556e authored by Johann's avatar Johann

Fix variance overflow

In the variance calculations the difference is summed and later squared.
When the sum exceeds sqrt(2^31) the value is treated as a negative when
it is shifted which gives incorrect results.

To fix this we cast the result of the multiplication as unsigned.

The alternative fix is to shift sum down by 4 before multiplying.
However that will reduce precision.

For 16x16 blocks the maximum sum is 65280 and sqrt(2^31) is 46340 (and
change).

PPC change is untested.

Change-Id: I1bad27ea0720067def6d71a6da5f789508cec265
parent 2e0d5531
......@@ -144,7 +144,7 @@ loop
ldr r6, [sp, #40] ; get address of sse
mul r0, r8, r8 ; sum * sum
str r11, [r6] ; store sse
sub r0, r11, r0, asr #8 ; return (sse - ((sum * sum) >> 8))
sub r0, r11, r0, lsr #8 ; return (sse - ((sum * sum) >> 8))
ldmfd sp!, {r4-r12, pc}
......
......@@ -169,7 +169,7 @@ loop
ldr r6, [sp, #40] ; get address of sse
mul r0, r8, r8 ; sum * sum
str r11, [r6] ; store sse
sub r0, r11, r0, asr #8 ; return (sse - ((sum * sum) >> 8))
sub r0, r11, r0, lsr #8 ; return (sse - ((sum * sum) >> 8))
ldmfd sp!, {r4-r12, pc}
......
......@@ -210,7 +210,7 @@ loop
ldr r6, [sp, #40] ; get address of sse
mul r0, r8, r8 ; sum * sum
str r11, [r6] ; store sse
sub r0, r11, r0, asr #8 ; return (sse - ((sum * sum) >> 8))
sub r0, r11, r0, lsr #8 ; return (sse - ((sum * sum) >> 8))
ldmfd sp!, {r4-r12, pc}
......
......@@ -171,7 +171,7 @@ loop
ldr r6, [sp, #40] ; get address of sse
mul r0, r8, r8 ; sum * sum
str r11, [r6] ; store sse
sub r0, r11, r0, asr #8 ; return (sse - ((sum * sum) >> 8))
sub r0, r11, r0, lsr #8 ; return (sse - ((sum * sum) >> 8))
ldmfd sp!, {r4-r12, pc}
......
......@@ -77,14 +77,14 @@ variance16x16_neon_loop
;vmov.32 r1, d1[0]
;mul r0, r0, r0
;str r1, [r12]
;sub r0, r1, r0, asr #8
;sub r0, r1, r0, lsr #8
;sum is in [-255x256, 255x256]. sumxsum is 32-bit. Shift to right should
;have sign-bit exension, which is vshr.s. Have to use s32 to make it right.
; while sum is signed, sum * sum is always positive and must be treated as
; unsigned to avoid propagating the sign bit.
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [r12] ;store sse
vshr.s32 d10, d10, #8
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #8
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
bx lr
......@@ -145,8 +145,8 @@ variance16x8_neon_loop
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [r12] ;store sse
vshr.s32 d10, d10, #7
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #7
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
bx lr
......@@ -200,8 +200,8 @@ variance8x16_neon_loop
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [r12] ;store sse
vshr.s32 d10, d10, #7
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #7
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
bx lr
......@@ -265,8 +265,8 @@ variance8x8_neon_loop
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [r12] ;store sse
vshr.s32 d10, d10, #6
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #6
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
bx lr
......
......@@ -405,8 +405,8 @@ sub_pixel_variance16x16_neon_loop
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [r6] ;store sse
vshr.s32 d10, d10, #8
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #8
vsub.u32 d0, d1, d10
add sp, sp, #528
vmov.32 r0, d0[0] ;return
......
......@@ -112,8 +112,8 @@ vp8_filt_fpo16x16s_4_0_loop_neon
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [lr] ;store sse
vshr.s32 d10, d10, #8
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #8
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
pop {pc}
......@@ -208,8 +208,8 @@ vp8_filt_spo16x16s_0_4_loop_neon
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [lr] ;store sse
vshr.s32 d10, d10, #8
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #8
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
pop {pc}
......@@ -327,8 +327,8 @@ vp8_filt16x16s_4_4_loop_neon
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [lr] ;store sse
vshr.s32 d10, d10, #8
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #8
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
pop {pc}
......@@ -560,8 +560,8 @@ sub_pixel_variance16x16s_neon_loop
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [lr] ;store sse
vshr.s32 d10, d10, #8
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #8
vsub.u32 d0, d1, d10
add sp, sp, #256
vmov.32 r0, d0[0] ;return
......
......@@ -206,8 +206,8 @@ sub_pixel_variance8x8_neon_loop
vmull.s32 q5, d0, d0
vst1.32 {d1[0]}, [lr] ;store sse
vshr.s32 d10, d10, #6
vsub.s32 d0, d1, d10
vshr.u32 d10, d10, #6
vsub.u32 d0, d1, d10
vmov.32 r0, d0[0] ;return
pop {r4-r5, pc}
......
......@@ -98,7 +98,7 @@
stw r4, 0(r7) ;# sse
mullw r3, r3, r3 ;# sum*sum
srawi r3, r3, \DS ;# (sum*sum) >> DS
srlwi r3, r3, \DS ;# (sum*sum) >> DS
subf r3, r3, r4 ;# sse - ((sum*sum) >> DS)
.endm
......@@ -142,7 +142,7 @@
stw r4, 0(r7) ;# sse
mullw r3, r3, r3 ;# sum*sum
srawi r3, r3, \DS ;# (sum*sum) >> 8
srlwi r3, r3, \DS ;# (sum*sum) >> 8
subf r3, r3, r4 ;# sse - ((sum*sum) >> 8)
.endm
......@@ -367,7 +367,7 @@ vp8_variance4x4_ppc:
stw r4, 0(r7) ;# sse
mullw r3, r3, r3 ;# sum*sum
srawi r3, r3, 4 ;# (sum*sum) >> 4
srlwi r3, r3, 4 ;# (sum*sum) >> 4
subf r3, r3, r4 ;# sse - ((sum*sum) >> 4)
epilogue
......
......@@ -157,7 +157,7 @@
stw r4, 0(r9) ;# sse
mullw r3, r3, r3 ;# sum*sum
srawi r3, r3, \DS ;# (sum*sum) >> 8
srlwi r3, r3, \DS ;# (sum*sum) >> 8
subf r3, r3, r4 ;# sse - ((sum*sum) >> 8)
.endm
......
......@@ -75,7 +75,7 @@ unsigned int vp8_variance16x16_c(
variance(src_ptr, source_stride, ref_ptr, recon_stride, 16, 16, &var, &avg);
*sse = var;
return (var - ((avg * avg) >> 8));
return (var - ((unsigned int)(avg * avg) >> 8));
}
unsigned int vp8_variance8x16_c(
......@@ -91,7 +91,7 @@ unsigned int vp8_variance8x16_c(
variance(src_ptr, source_stride, ref_ptr, recon_stride, 8, 16, &var, &avg);
*sse = var;
return (var - ((avg * avg) >> 7));
return (var - ((unsigned int)(avg * avg) >> 7));
}
unsigned int vp8_variance16x8_c(
......@@ -107,7 +107,7 @@ unsigned int vp8_variance16x8_c(
variance(src_ptr, source_stride, ref_ptr, recon_stride, 16, 8, &var, &avg);
*sse = var;
return (var - ((avg * avg) >> 7));
return (var - ((unsigned int)(avg * avg) >> 7));
}
......@@ -124,7 +124,7 @@ unsigned int vp8_variance8x8_c(
variance(src_ptr, source_stride, ref_ptr, recon_stride, 8, 8, &var, &avg);
*sse = var;
return (var - ((avg * avg) >> 6));
return (var - ((unsigned int)(avg * avg) >> 6));
}
unsigned int vp8_variance4x4_c(
......@@ -140,7 +140,7 @@ unsigned int vp8_variance4x4_c(
variance(src_ptr, source_stride, ref_ptr, recon_stride, 4, 4, &var, &avg);
*sse = var;
return (var - ((avg * avg) >> 4));
return (var - ((unsigned int)(avg * avg) >> 4));
}
......
......@@ -91,7 +91,7 @@ unsigned int vp8_variance4x4_mmx(
vp8_get4x4var_mmx(src_ptr, source_stride, ref_ptr, recon_stride, &var, &avg) ;
*sse = var;
return (var - ((avg * avg) >> 4));
return (var - ((unsigned int)(avg * avg) >> 4));
}
......@@ -108,7 +108,7 @@ unsigned int vp8_variance8x8_mmx(
vp8_get8x8var_mmx(src_ptr, source_stride, ref_ptr, recon_stride, &var, &avg) ;
*sse = var;
return (var - ((avg * avg) >> 6));
return (var - ((unsigned int)(avg * avg) >> 6));
}
......@@ -153,7 +153,7 @@ unsigned int vp8_variance16x16_mmx(
var = sse0 + sse1 + sse2 + sse3;
avg = sum0 + sum1 + sum2 + sum3;
*sse = var;
return (var - ((avg * avg) >> 8));
return (var - ((unsigned int)(avg * avg) >> 8));
}
unsigned int vp8_variance16x8_mmx(
......@@ -172,7 +172,7 @@ unsigned int vp8_variance16x8_mmx(
var = sse0 + sse1;
avg = sum0 + sum1;
*sse = var;
return (var - ((avg * avg) >> 7));
return (var - ((unsigned int)(avg * avg) >> 7));
}
......@@ -194,7 +194,7 @@ unsigned int vp8_variance8x16_mmx(
avg = sum0 + sum1;
*sse = var;
return (var - ((avg * avg) >> 7));
return (var - ((unsigned int)(avg * avg) >> 7));
}
......
......@@ -148,7 +148,7 @@ unsigned int vp8_variance4x4_wmt(
vp8_get4x4var_mmx(src_ptr, source_stride, ref_ptr, recon_stride, &var, &avg) ;
*sse = var;
return (var - ((avg * avg) >> 4));
return (var - ((unsigned int)(avg * avg) >> 4));
}
......@@ -165,7 +165,7 @@ unsigned int vp8_variance8x8_wmt
vp8_get8x8var_sse2(src_ptr, source_stride, ref_ptr, recon_stride, &var, &avg) ;
*sse = var;
return (var - ((avg * avg) >> 6));
return (var - ((unsigned int)(avg * avg) >> 6));
}
......@@ -220,7 +220,7 @@ unsigned int vp8_variance16x8_wmt
var = sse0 + sse1;
avg = sum0 + sum1;
*sse = var;
return (var - ((avg * avg) >> 7));
return (var - ((unsigned int)(avg * avg) >> 7));
}
......@@ -241,7 +241,7 @@ unsigned int vp8_variance8x16_wmt
var = sse0 + sse1;
avg = sum0 + sum1;
*sse = var;
return (var - ((avg * avg) >> 7));
return (var - ((unsigned int)(avg * avg) >> 7));
}
......
......@@ -112,7 +112,7 @@ unsigned int vp8_sub_pixel_variance16x16_ssse3
}
*sse = xxsum0;
return (xxsum0 - ((xsum0 * xsum0) >> 8));
return (xxsum0 - ((unsigned int)(xsum0 * xsum0) >> 8));
}
unsigned int vp8_sub_pixel_variance16x8_ssse3
......@@ -161,5 +161,5 @@ unsigned int vp8_sub_pixel_variance16x8_ssse3
}
*sse = xxsum0;
return (xxsum0 - ((xsum0 * xsum0) >> 7));
return (xxsum0 - ((unsigned int)(xsum0 * xsum0) >> 7));
}
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