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commit 656b84c2ef525e3b69802c9057c5897e327b0332
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Author: Wilco Dijkstra <wdijkstr@arm.com>
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Date: Thu Aug 7 16:29:55 2014 +0000
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This patch adds new function libc_feholdsetround_noex_aarch64_ctx, enabling
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further optimization. libc_feholdsetround_aarch64_ctx now only needs to
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read the FPCR in the typical case, avoiding a redundant FPSR read.
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Performance results show a good improvement (5-10% on sin()) on cores with
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expensive FPCR/FPSR instructions.
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diff --git a/ports/sysdeps/aarch64/fpu/math_private.h b/ports/sysdeps/aarch64/fpu/math_private.h
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index 023c9d0..b13c030 100644
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--- a/ports/sysdeps/aarch64/fpu/math_private.h
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+++ b/ports/sysdeps/aarch64/fpu/math_private.h
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@@ -228,12 +228,9 @@ static __always_inline void
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libc_feholdsetround_aarch64_ctx (struct rm_ctx *ctx, int r)
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{
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fpu_control_t fpcr;
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- fpu_fpsr_t fpsr;
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int round;
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_FPU_GETCW (fpcr);
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- _FPU_GETFPSR (fpsr);
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- ctx->env.__fpsr = fpsr;
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/* Check whether rounding modes are different. */
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round = (fpcr ^ r) & _FPU_FPCR_RM_MASK;
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@@ -264,6 +261,33 @@ libc_feresetround_aarch64_ctx (struct rm_ctx *ctx)
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#define libc_feresetroundl_ctx libc_feresetround_aarch64_ctx
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static __always_inline void
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+libc_feholdsetround_noex_aarch64_ctx (struct rm_ctx *ctx, int r)
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+{
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+ fpu_control_t fpcr;
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+ fpu_fpsr_t fpsr;
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+ int round;
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+
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+ _FPU_GETCW (fpcr);
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+ _FPU_GETFPSR (fpsr);
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+ ctx->env.__fpsr = fpsr;
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+
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+ /* Check whether rounding modes are different. */
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+ round = (fpcr ^ r) & _FPU_FPCR_RM_MASK;
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+ ctx->updated_status = round != 0;
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+
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+ /* Set the rounding mode if changed. */
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+ if (__glibc_unlikely (round != 0))
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+ {
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+ ctx->env.__fpcr = fpcr;
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+ _FPU_SETCW (fpcr ^ round);
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+ }
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+}
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+
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+#define libc_feholdsetround_noex_ctx libc_feholdsetround_noex_aarch64_ctx
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+#define libc_feholdsetround_noexf_ctx libc_feholdsetround_noex_aarch64_ctx
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+#define libc_feholdsetround_noexl_ctx libc_feholdsetround_noex_aarch64_ctx
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+
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+static __always_inline void
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libc_feresetround_noex_aarch64_ctx (struct rm_ctx *ctx)
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{
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/* Restore the rounding mode if updated. */
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