code review 10368043: runtime: do not generate code during runtime in windows...

src/pkg/runtime/sys_windows_386.s

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 #include "zasm_GOOS_GOARCH.h"
 
 // void runtime·asmstdcall(void *c);
 TEXT runtime·asmstdcall(SB),7,$0
         MOVL    c+0(FP), BX
 
@@ skipping 173 matching lines @@
         // set up SEH frame again
         PUSHL   $runtime·sigtramp(SB)
         PUSHL   0(FS)
         MOVL    SP, 0(FS)
 
         // determine index into runtime·cbctxts table
         SUBL    $runtime·callbackasm(SB), AX
         MOVL    $0, DX
         MOVL    $5, BX  // divide by 5 because each call instruction in runtime·callbacks is 5 bytes long
         DIVL    BX,
-        SUBL    $1, AX
 
         // find correspondent runtime·cbctxts table entry
-        MOVL    $4, BX
-        MULL    BX
-        ADDL    runtime·cbctxts(SB), AX
-        MOVL    (AX), BX
+        MOVL    runtime·cbctxts(SB), BX
+        MOVL    -4(BX)(AX*4), BX
 
         // extract callback context
         MOVL    cbctxt_gobody(BX), AX
         MOVL    cbctxt_argsize(BX), DX
 
         // preserve whatever's at the memory location that
         // the callback will use to store the return value
         PUSHL   0(CX)(DX*1)
 
         // extend argsize by size of return value
@@ skipping 154 matching lines @@
         MOVL    BP, SP
         RET
 
 // This function requires 4 bytes of stack,
 // to simulate what calling NtWaitForSingleObject will use.
 // (It is just a CALL to the system call dispatch.)
 // If the linker okays the call to checkstack4 (a NOSPLIT function)
 // then the call to NtWaitForSingleObject is okay too.
 TEXT checkstack4<>(SB),7,$4
         RET