From patchwork Tue Aug 15 19:55:41 2017
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Date: Tue, 15 Aug 2017 12:55:41 -0700
From: "H.J. Lu" <hongjiu.lu@intel.com>
To: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH] x86-64: Put L(SP_INF_0) in .rodata.cst4 section [BZ
	#21955]
Message-ID: <20170815195541.GA19812@gmail.com>
Reply-To: "H.J. Lu" <hjl.tools@gmail.com>
References: <20170815173855.GA19119@gmail.com>
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On Tue, Aug 15, 2017 at 10:38:55AM -0700, H.J. Lu wrote:
> sysdeps/x86_64/fpu/e_expf.S has
> 
>         /* Here if |x| is Inf */
>         lea     L(SP_INF_0)(%rip), %rdx /* depending on sign of x: */
>         movss   (%rdx,%rax,4), %xmm0    /* return zero or Inf */
>         ret
> ...
>          .section .rodata.cst8,"aM",@progbits,8
> ...
>         .p2align 2
> L(SP_INF_0):
>         .long   0x7f800000      /* single precision Inf */
>         .long   0               /* single precision zero */
>         .type L(SP_INF_0), @object
>         ASM_SIZE_DIRECTIVE(L(SP_INF_0))
> 
> Since L(SP_INF_0) is accessed as an array of 4-byte elements, it should
> be placed in
> 
> 	.section .rodata.cst4,"aM",@progbits,4
> 
> Tested on x86-64.  Any comments?
> 
> H.J.
> ---
> 	[BZ #21955]
> 	* sysdeps/x86_64/fpu/e_expf.S (L(SP_INF_0)): Place it in
> 	.rodata.cst4 section.

L(SP_RANGE) has the same issue.  This updated patch fixes both.

H.J.
---
sysdeps/x86_64/fpu/e_expf.S has

        lea     L(SP_RANGE)(%rip), %rdx /* load over/underflow bound */
        cmpl    (%rdx,%rax,4), %ecx     /* |x|<under/overflow bound ? */
...
        /* Here if |x| is Inf */
        lea     L(SP_INF_0)(%rip), %rdx /* depending on sign of x: */
        movss   (%rdx,%rax,4), %xmm0    /* return zero or Inf */
        ret
...
         .section .rodata.cst8,"aM",@progbits,8
...
        .p2align 2
L(SP_RANGE): /* single precision overflow/underflow bounds */
        .long   0x42b17217      /* if x>this bound, then result overflows */
        .long   0x42cff1b4      /* if x<this bound, then result underflows */
        .type L(SP_RANGE), @object
        ASM_SIZE_DIRECTIVE(L(SP_RANGE))

        .p2align 2
L(SP_INF_0):
        .long   0x7f800000      /* single precision Inf */
        .long   0               /* single precision zero */
        .type L(SP_INF_0), @object
        ASM_SIZE_DIRECTIVE(L(SP_INF_0))

Since L(SP_RANGE) and L(SP_INF_0) are accessed as arrays of 4-byte
elements, they should be placed in .rodata.cst4 section.

	[BZ #21955]
	* sysdeps/x86_64/fpu/e_expf.S (L(SP_RANGE)): Place it in
	.rodata.cst4 section.
	(L(SP_INF_0)): Likewise.
---
 sysdeps/x86_64/fpu/e_expf.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sysdeps/x86_64/fpu/e_expf.S b/sysdeps/x86_64/fpu/e_expf.S
index 4fd2bb1fb5..29e421b4bd 100644
--- a/sysdeps/x86_64/fpu/e_expf.S
+++ b/sysdeps/x86_64/fpu/e_expf.S
@@ -297,6 +297,7 @@ L(DP_P0): /* double precision polynomial coefficient P0 */
 	.type L(DP_P0), @object
 	ASM_SIZE_DIRECTIVE(L(DP_P0))
 
+	.section .rodata.cst4,"aM",@progbits,4
 	.p2align 2
 L(SP_RANGE): /* single precision overflow/underflow bounds */
 	.long	0x42b17217	/* if x>this bound, then result overflows */
@@ -311,7 +312,6 @@ L(SP_INF_0):
 	.type L(SP_INF_0), @object
 	ASM_SIZE_DIRECTIVE(L(SP_INF_0))
 
-	.section .rodata.cst4,"aM",@progbits,4
 	.p2align 2
 L(SP_RS): /* single precision 2^23+2^22 */
 	.long	0x4b400000