Currently jsopcode.tbl defines that JSOP_LEAVEBLOCK and JSOP_LEAVEBLOCKEXPR use 0 stack slots when in reality they pop the local variable from stack. This discrepancy forces the emitter and the decompiler to special-case handling of the bytecodes and explicitly update the stack. Thus I suggest to set the use counts for the bytecodes to -1 so they can be handles in the same way as the rest of stack-variadic operations. This should allow to have a single helper function to get the real use counts for the variadic bytecodes based on their operands.

To ensure uniform handling of stack-variadic bytecodes, the patch changes: -OPDEF(JSOP_LEAVEBLOCK, 200,"leaveblock", NULL, 3, 0, 0, 0, JOF_UINT16) +OPDEF(JSOP_LEAVEBLOCK, 200,"leaveblock", NULL, 3, -1, 0, 0, JOF_UINT16) -OPDEF(JSOP_LEAVEBLOCKEXPR,215,"leaveblockexpr",NULL, 3, 0, 0, 1, JOF_UINT1 6) +OPDEF(JSOP_LEAVEBLOCKEXPR,215,"leaveblockexpr",NULL, 3, -1, 1, 1, JOF_UINT16) This allowed to have the single helper function, js_GetVariableStackUseLength, that used both by the emitter and the decompiler avoiding code duplication. I aslo changed: -OPDEF(JSOP_ENTERBLOCK, 199,"enterblock", NULL, 3, 0, 0, 0, JOF_OBJECT) +OPDEF(JSOP_ENTERBLOCK, 199,"enterblock", NULL, 3, 0, -1, 0, JOF_OBJECT) This way UpdateDepth in jsemit.cpp could check for a negative ndef and update the stack based on the block object. Yet another change is: -OPDEF(JSOP_RETSUB, 115,"retsub", NULL, 1, 0, 0, 0, JOF_BYTE) +OPDEF(JSOP_RETSUB, 115,"retsub", NULL, 1, 2, 0, 0, JOF_BYTE) -OPDEF(JSOP_FINALLY, 134,"finally", NULL, 1, 0, 0, 0, JOF_BYTE) +OPDEF(JSOP_FINALLY, 134,"finally", NULL, 1, 0, 2, 0, JOF_BYTE) This allowed to remove any special handling of JSOP_FINALLY and JSOP_RETSUB when updating the stack depth.

fixing proper dependency

Comment on attachment 332616 [details] [diff] [review] v1 Sorry for the delay in review.

Ooh, would this fix our undiagnosed Windows-only bug in turning on JSOP_NEWARRAY or JSOP_CONCAT? /be

Comment on attachment 332616 [details] [diff] [review] v1 >+/* >+ * Find the number of stack slots that the bytecode uses when JSCodeSpec.nuses >+ * is -1. Suggest "Find the number of stack slots used by a variadic opcode such as JSOP_CALL or JSOP_NEWARRAY (for such ops, JSCodeSpec.nuses is -1)." r=me with that, thanks. /be

landed - http://hg.mozilla.org/mozilla-central/rev/774fe6f69796