[NativeAOT] fix debug assert on large number of virtual methods #77106
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According to the ARM docs for this op code: https://developer.arm.com/documentation/ddi0596/2020-12/Base-Instructions/LDR--immediate---Load-Register--immediate--?lang=en > For the 64-bit variant: is the optional positive immediate byte offset, a multiple of 8 in the range 0 to 32760, defaulting to 0 and encoded in the "imm12" field as <pimm>/8. You can see that once the offset has been devided by 8, it will be in the range [0, 4095], which will fit in the 12 bits allocated for the offset.
ghost
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jkotas
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Oct 17, 2022
| @@ -63,7 +63,7 @@ public void EmitLDR(Register regDst, Register regAddr) | |||
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| public void EmitLDR(Register regDst, Register regSrc, int offset) | |||
| { | |||
| Debug.Assert(offset >= -255 && offset <= 4095); | |||
| Debug.Assert(offset >= -255 && offset <= 32760); | |||
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We may want to throw new NotImplementedException(); when the offset is too big. I think it is possible to construct cases where the offset is too big. It is better to throw exception than emit bad code silently.
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According to the ARM docs for this op code:
https://developer.arm.com/documentation/ddi0596/2020-12/Base-Instructions/LDR--immediate---Load-Register--immediate--?lang=en
I have a program that reproduces the problem. It is just a class with 1000 virtual properties and a RD.xml file to root them all. The actual program I was trying to compile when I encountered the problem was Microsoft.macos.dll. There are some classes with a large number of virtual methods in that assembly.