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authorBjörn Gustavsson <[email protected]>2018-09-02 08:42:51 +0200
committerBjörn Gustavsson <[email protected]>2018-09-03 09:09:41 +0200
commit5801fcb2b36e04c433dcf0b90a8c47b86e34fc07 (patch)
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parent860ee1974caac4447dcbd7f9d7c27a252170d7a3 (diff)
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ops.tab: Fix potentially unsafe optimization of raise/2
The operands for the raise/2 instruction are almost always in x(2) and x(1). Therefore the loader translates the raise/2 instruction to an i_raise/0 instruction which uses the values in x(2) and x(1). If the operands happens to be in other registers, the loader inserts move/2 instruction to move them to x(2) and x(1). The problem is that x(3) is used as a temporary register when generating the move/2 instructions. That is unsafe if the Value operand for raise/2 is x(3). Thus: raise x(0) x(3) will be translated to: move x(0) x(3) move x(3) x(1) move x(3) x(2) i_raise The Trace will be written to both x(2) and x(1). The current compiler will never use x(3) for the Value operand, so there is no need to patch previous releases. But a future compiler version might allocate registers differently.
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