The CL #35651 (https://codereview.chromium.org/1858323003) exposed one hiden issue in RunTruncateFloat32ToUint32 test cases and X87 failed at it.
Here is the issue in RunTruncateFloat32ToUint32:
For float input = static_cast<float>(*i), the x87 GCC would optimize the input viariable in float floating register for release build.
The problem is:
SSE float register has single precision rounding semantic While X87 register hasn't when directly use floating register value. It will cause the value of input viariable has
different precision for IA32 and X87 port. So static_cast<uint32_t>(input) will be different for IA32 and X87 port too.
This led to CHECK_EQ(static_cast<uint32_t>(input), m.Call(input)) fail although V8 turbofan JITTed code m.Call(input) has exactly same result in both X87 and IA32 port.
So we add the following sentence to do type cast to keep the single precision for RunTruncateFloat32ToUint32 by forcing the input viariable get value from memory insread of
floating register.
Such as: volatile float input = static_cast<float>(*i).
BUG=
Review URL: https://codereview.chromium.org/1905883002
Cr-Commit-Position: refs/heads/master@{#35689}
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