T0b1/wasmtime
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

x86_32: fix stack_addr encoding.

Browse Source 
Consider this testcase:

    target i686
    function u0:0() -> i32 system_v {
        ss0 = explicit_slot 0
    block0:
        v2 = stack_addr.i32 ss0
        return v2
    }

Before this commit, in 32-bit mode the x86 backend would generate
incorrect code for stack addresses:

     0:   55                      push    ebp
     1:   89 e5                   mov     ebp, esp
     3:   83 ec 08                sub     esp, 8
     6:   8d 44 24 00             lea     eax, [esp]
     a:   00 00                   add     byte ptr [eax], al
     c:   00 83 c4 08 5d c3       add     byte ptr [ebx - 0x3ca2f73c], al

This happened because the ModRM byte indicated a disp8 encoding, but
the instruction actually used a disp32 encoding. After this commit,
correct code is generated:

     0:   55                      push    ebp
     1:   89 e5                   mov     ebp, esp
     3:   83 ec 08                sub     esp, 8
     6:   8d 84 24 00 00 00 00    lea     eax, [esp]
     d:   83 c4 08                add     esp, 8
    10:   5d                      pop     ebp
    11:   c3                      ret
This commit is contained in:
whitequark
2020-05-29 15:27:34 +00:00
committed by iximeow
parent 09ccdc9285
commit a180b5b393
3 changed files with 37 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
cranelift/filetests/filetests/isa/x86/stack-addr32.clif Normal file
View File

@@ -0,0 +1,33 @@
; binary emission of stack address instructions on i686.
test binemit
set opt_level=none
target i686 haswell
; The binary encodings can be verified with the command:
;
; sed -ne 's/^ *; asm: *//p' filetests/isa/x86/stack-addr32.clif | llvm-mc -show-encoding -triple=i686
;
function %stack_addr() {
ss0 = incoming_arg 8, offset 0
ss1 = incoming_arg 1024, offset -1024
ss2 = incoming_arg 1024, offset -2048
ss3 = incoming_arg 8, offset -2056
ss4 = explicit_slot 8, offset 0
ss5 = explicit_slot 8, offset 1024
block0:
[-,%rcx] v0 = stack_addr.i32 ss0 ; bin: 8d 8c 24 00000808
[-,%rcx] v1 = stack_addr.i32 ss1 ; bin: 8d 8c 24 00000408
[-,%rcx] v2 = stack_addr.i32 ss2 ; bin: 8d 8c 24 00000008
[-,%rcx] v3 = stack_addr.i32 ss3 ; bin: 8d 8c 24 00000000
[-,%rcx] v4 = stack_addr.i32 ss4 ; bin: 8d 8c 24 00000808
[-,%rcx] v5 = stack_addr.i32 ss5 ; bin: 8d 8c 24 00000c08
[-,%rcx] v20 = stack_addr.i32 ss4+1 ; bin: 8d 8c 24 00000809
[-,%rcx] v21 = stack_addr.i32 ss4+2 ; bin: 8d 8c 24 0000080a
[-,%rcx] v22 = stack_addr.i32 ss4+2048 ; bin: 8d 8c 24 00001008
[-,%rcx] v23 = stack_addr.i32 ss4-4096 ; bin: 8d 8c 24 fffff808
return
}