[LLVMdev] Stange behavior in fp arithmetics on x86 (bug possibly) (original) (raw)
Dmitry Borisenkov d.borisenkov at samsung.com
Wed Oct 8 01:36:04 PDT 2014
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Hi, Joerg
Both of the examples were compiled ./llc -march=x86 -O3 fpfail.ll (i386). I've double checked it.
Kind regards, Dmitry Borisenkov
-----Original Message----- From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Joerg Sonnenberger Sent: Tuesday, October 07, 2014 10:45 PM To: llvmdev at cs.uiuc.edu Subject: Re: [LLVMdev] Stange behavior in fp arithmetics on x86 (bug possibly)
On Tue, Oct 07, 2014 at 09:50:37PM +0400, Dmitry Borisenkov wrote:
I'm not an expert neither in llvm nor in x86 nor in IEEE standard for floating point numbers, thus any of my following assumptions maybe wrong. If so, I will be grateful if you clarify me what's goes wrong. But if my guesses are correct we possibly have a bug in fp arithmetics on x86.
Are you targetting the same backend? i386 (32bit mode) uses FPU registers for argument passing and return values, x86_64 / amd64 (64bit mode) uses SSE registers for float/double values and FPU registers for long double. The error on retl makes me think the second example is compiled for i386, while the first example looks more like x86_64.
Joerg
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