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| author | Kartik Agaram <vc@akkartik.com> | 2020-03-06 18:31:14 -0800 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2020-03-06 18:34:27 -0800 |
| commit | 8f256f1f2ee6a2a49816dd23d26cd120f526bf0b (patch) | |
| tree | 314294998b527980cdf85ecb51386642bfbe3af4 /apps | |
| parent | 4c19dd3968d2ce733073774867d97cc96b4277e6 (diff) | |
| download | mu-8f256f1f2ee6a2a49816dd23d26cd120f526bf0b.tar.gz | |
6090 - new instruction: multiply by immediate
This is a 3-operand instruction: r32 = rm32 * imm32 It looks like https://c9x.me/x86/html/file_module_x86_id_138.html has a bug, implying the same opcode supports a 2-operand version. I don't see that in the Intel manual pdf, or at alternative sites like https://www.felixcloutier.com/x86/imul Native runs seem to validate my understanding. In the process I also fixed a bug in the existing multiply instruction 0f af: the only flags it sets are OF and CF. The other existing multiply instruction f7 was doing things right.
Diffstat (limited to 'apps')
| -rwxr-xr-x | apps/ex14 | bin | 0 -> 213 bytes | |||
| -rw-r--r-- | apps/ex14.subx | 26 |
2 files changed, 26 insertions, 0 deletions
diff --git a/apps/ex14 b/apps/ex14 new file mode 100755 index 00000000..b2792177 --- /dev/null +++ b/apps/ex14 Binary files differdiff --git a/apps/ex14.subx b/apps/ex14.subx new file mode 100644 index 00000000..74dd3809 --- /dev/null +++ b/apps/ex14.subx @@ -0,0 +1,26 @@ +# Multiply 2 numbers. +# +# To run: +# $ ./bootstrap translate init.linux apps/ex14.subx -o apps/ex14 +# $ ./bootstrap run apps/ex14 +# Expected result: +# $ echo $? +# 6 + +== code +# instruction effective address register displacement immediate +# . op subop mod rm32 base index scale r32 +# . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes + +Entry: + b8/copy-to-eax 1/imm32 + b9/copy-to-ecx 2/imm32 + bb/copy-to-ebx 3/imm32 + + 69/multiply 3/mod/direct 1/rm32/ecx . . . 3/r32/ebx 3/imm32 # ebx = ecx * 3 + +$exit: + # exit(ebx) + e8/call syscall_exit/disp32 + +# . . vim:nowrap:textwidth=0 |