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Define JumpImmediateRange on ARM64.

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There are comments in the code suggesting that we've made plans at some
point to handle very far jumps via patching + indirect jumps, but all of
those comments are TODO/FIXME. Absent such a strategy, the furthest jump
is 2^27-1 bytes, and we need to define JumpImmediateRange to reflect
that.
This commit is contained in:
Lars T Hansen 2019-07-20 15:43:01 +02:00 • committed by Roy Tam
commit b97da34a21
1 changed files with 6 additions and 4 deletions
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10
js/src/jit/arm64/Architecture-arm64.h
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@ -299,10 +299,12 @@ static const uint32_t ION_FRAME_SLACK_SIZE = 24;
static const uint32_t ShadowStackSpace = 0;
// TODO:
// This constant needs to be updated to account for whatever near/far branching
// strategy is used by ARM64.
static const uint32_t JumpImmediateRange = UINT32_MAX;
// When our only strategy for far jumps is to encode the offset directly, and
// not insert any jump islands during assembly for even further jumps, then the
// architecture restricts us to -2^27 .. 2^27-4, to fit into a signed 28-bit
// value. We further reduce this range to allow the far-jump inserting code to
// have some breathing room.
static const uint32_t JumpImmediateRange = ((1 << 27) - (20 * 1024 * 1024));
static const uint32_t ABIStackAlignment = 16;
static const uint32_t CodeAlignment = 16;