Commit fea3556e by 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.

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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