Emit always, even when exceeding.

klauspost · Dec 7, 2020 · 1f39cf5 · 1f39cf5
1 parent 966a9d2
commit 1f39cf5
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Showing 2 changed files with 50 additions and 22 deletions.
diff --git a/s2/_generate/gen.go b/s2/_generate/gen.go
@@ -667,6 +667,10 @@ func (o options) genEncodeBlockAsm(name string, tableBits, skipLog, hashBytes, m
 	// Bail if we exceed the maximum size.
 	// if d+len(src)-nextEmitL > dstLimitPtrQ {	return 0
 	{
+		// If we didn't output anything, we always have space to emit as is.
+		CMPL(nextEmitL, U8(0))
+		JEQ(LabelRef("emit_remainder_ok_" + name))
+
 		// remain = len(src) - nextEmit
 		remain := GP64()
 		MOVQ(lenSrcQ, remain)
@@ -678,12 +682,10 @@ func (o options) genEncodeBlockAsm(name string, tableBits, skipLog, hashBytes, m
 		LEAQ(Mem{Base: dst, Index: remain, Scale: 1, Disp: literalMaxOverhead}, dstExpect)
 		CMPQ(dstExpect, dstLimitPtrQ)
 		JL(LabelRef("emit_remainder_ok_" + name))
-		ri, err := ReturnIndex(0).Resolve()
-		if err != nil {
-			panic(err)
-		}
-		MOVQ(U32(0), ri.Addr)
-		RET()
+		// Emit as single literal block, overwriting what we have.
+		MOVL(U32(0), nextEmitL)
+		Load(Param("dst").Base(), dst)
+		Load(Param("src").Base(), src)
 		Label("emit_remainder_ok_" + name)
 	}
 	// emitLiteral(dst[d:], src[nextEmitL:])
@@ -785,6 +787,8 @@ type hashGen struct {
 	bytes     int
 	tablebits int
 	mulreg    reg.GPVirtual
+	vbmireg   reg.GPVirtual
+	vbmi      bool
 }
 
 // hashN uses multiply to get a 'output' hash on the hash of the lowest 'bytes' bytes in value.

diff --git a/s2/encodeblock_amd64.s b/s2/encodeblock_amd64.s
@@ -1047,13 +1047,16 @@ match_nolit_dst_ok_encodeBlockAsm:
 	JMP   search_loop_encodeBlockAsm
 
 emit_remainder_encodeBlockAsm:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeBlockAsm
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeBlockAsm
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeBlockAsm:
 	MOVQ src_len+32(FP), CX
@@ -1982,13 +1985,16 @@ match_nolit_dst_ok_encodeBlockAsm12B:
 	JMP   search_loop_encodeBlockAsm12B
 
 emit_remainder_encodeBlockAsm12B:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeBlockAsm12B
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeBlockAsm12B
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeBlockAsm12B:
 	MOVQ src_len+32(FP), CX
@@ -2898,13 +2904,16 @@ match_nolit_dst_ok_encodeBlockAsm10B:
 	JMP   search_loop_encodeBlockAsm10B
 
 emit_remainder_encodeBlockAsm10B:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeBlockAsm10B
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeBlockAsm10B
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeBlockAsm10B:
 	MOVQ src_len+32(FP), CX
@@ -3798,13 +3807,16 @@ match_nolit_dst_ok_encodeBlockAsm8B:
 	JMP   search_loop_encodeBlockAsm8B
 
 emit_remainder_encodeBlockAsm8B:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeBlockAsm8B
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeBlockAsm8B
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeBlockAsm8B:
 	MOVQ src_len+32(FP), CX
@@ -4669,13 +4681,16 @@ match_nolit_dst_ok_encodeSnappyBlockAsm:
 	JMP   search_loop_encodeSnappyBlockAsm
 
 emit_remainder_encodeSnappyBlockAsm:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeSnappyBlockAsm
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeSnappyBlockAsm
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeSnappyBlockAsm:
 	MOVQ src_len+32(FP), CX
@@ -5475,13 +5490,16 @@ match_nolit_dst_ok_encodeSnappyBlockAsm12B:
 	JMP   search_loop_encodeSnappyBlockAsm12B
 
 emit_remainder_encodeSnappyBlockAsm12B:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeSnappyBlockAsm12B
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeSnappyBlockAsm12B
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeSnappyBlockAsm12B:
 	MOVQ src_len+32(FP), CX
@@ -6262,13 +6280,16 @@ match_nolit_dst_ok_encodeSnappyBlockAsm10B:
 	JMP   search_loop_encodeSnappyBlockAsm10B
 
 emit_remainder_encodeSnappyBlockAsm10B:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeSnappyBlockAsm10B
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeSnappyBlockAsm10B
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeSnappyBlockAsm10B:
 	MOVQ src_len+32(FP), CX
@@ -7045,13 +7066,16 @@ match_nolit_dst_ok_encodeSnappyBlockAsm8B:
 	JMP   search_loop_encodeSnappyBlockAsm8B
 
 emit_remainder_encodeSnappyBlockAsm8B:
+	CMPL 12(SP), $0x00
+	JEQ  emit_remainder_ok_encodeSnappyBlockAsm8B
 	MOVQ src_len+32(FP), CX
 	SUBL 12(SP), CX
 	LEAQ 4(AX)(CX*1), CX
 	CMPQ CX, (SP)
 	JL   emit_remainder_ok_encodeSnappyBlockAsm8B
-	MOVQ $0x00000000, ret+48(FP)
-	RET
+	MOVL $0x00000000, 12(SP)
+	MOVQ dst_base+0(FP), AX
+	MOVQ src_base+24(FP), DX
 
 emit_remainder_ok_encodeSnappyBlockAsm8B:
 	MOVQ src_len+32(FP), CX