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[x64] Restore FP rounding mode after host callbacks

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Add MXCSR restore to the x64 GuestToHostThunk so host callbacks can't
leak their rounding state into subsequent guest FP operations.
This commit is contained in:
Herman S.
2026-03-23 12:01:03 +09:00
parent ecd7501029
commit 3747f5e282
2 changed files with 93 additions and 0 deletions
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6
src/xenia/cpu/backend/x64/x64_backend.cc
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@@ -753,6 +753,9 @@ GuestToHostThunk X64HelperEmitter::EmitGuestToHostThunk() {
call(rax);
EmitLoadVolatileRegs();
// Host callbacks may change MXCSR. Restore the guest scalar rounding mode
// so later guest FP ops observe the correct PPC rounding state.
vldmxcsr(GetBackendCtxPtr(offsetof(X64BackendContext, mxcsr_fpu)));
code_offsets.epilog = getSize();
@@ -801,6 +804,9 @@ GuestToHostThunk X64HelperEmitter::EmitGuestToHostThunk() {
call(rax);
EmitLoadVolatileRegs();
// Host callbacks may change MXCSR. Restore the guest scalar rounding mode
// so later guest FP ops observe the correct PPC rounding state.
vldmxcsr(GetBackendCtxPtr(offsetof(X64BackendContext, mxcsr_fpu)));
code_offsets.epilog = getSize();