commit | 037cff952caac336c73c2091eae04bc95cf5c01f | [log] [tgz] |
---|---|---|
author | Regis Crelier <regis@google.com> | Mon Oct 19 18:54:37 2020 +0000 |
committer | commit-bot@chromium.org <commit-bot@chromium.org> | Mon Oct 19 18:54:37 2020 +0000 |
tree | 7ed4c3edac4a49510393e904eb405fc031e60b4a | |
parent | da6c506f2c44162cfba1db5572520d9abc3729aa [diff] |
[VM/assembler] Use correct operand size in FieldAddress on arm64. This change prevents the scaled addressing mode to be wrongly applied by the assembler. Let's illustrate with an example: __ ldr(R1, FieldAddress(R1, target::Type::nullability_offset()), kUnsignedByte); Let's assume that target::Type::nullability_offset() == 57 (it is currently 61, but will be 57 in a forthcoming CL). FieldAddress substracts 1 and builds an Address with offset 56. The default operand size passed to Address is kDoubleWord, i.e. a scaling factor of 3. Because 56 == (56 >> 3) << 3, the scaled addressing mode is chosen with a scaled offset of 7, which would be correct for a kDoubleWord access, but not for a kUnsignedByte access. It is important to specify the same operand size in the instruction as in FieldAddress: __ ldr(R1, FieldAddress(R1, target::Type::nullability_offset(), kByte), kUnsignedByte); Change-Id: I46cf2b6ac103b2acec723189c88e211567b795af Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/167900 Reviewed-by: Ryan Macnak <rmacnak@google.com> Commit-Queue: RĂ©gis Crelier <regis@google.com>
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