From 024f701ca1dc69ff3d6a3d0ec727debc224018f0 Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Wed, 16 Nov 2016 10:21:22 +0000 Subject: [PATCH] Optimise CONCAT handling in emit_group_load The CONCAT handling in emit_group_load chooses between doing an extraction from a single component or forcing the whole thing to memory and extracting from there. The condition for the former (more efficient) option was: if ((bytepos == 0 && bytelen == slen0) || (bytepos != 0 && bytepos + bytelen <= slen)) On the one hand this seems dangerous, since the second line allows bit ranges that start in the first component and leak into the second. On the other hand it seems strange to allow references that start after the first byte of the second component but not those that start after the first byte of the first component. This led to a pessimisation of things like gcc.dg/builtins-54.c for hppa64-hp-hpux11.23. This patch simply checks whether the reference is contained within a single component. It also makes sure that we do an extraction on anything that doesn't span the whole component (even if it's constant). gcc/ 2016-11-15 Richard Sandiford Alan Hayward David Sherwood * expr.c (emit_group_load_1): Tighten check for whether an access involves only one operand of a CONCAT. Use extract_bit_field for constants if the bit range does span the whole operand. Co-Authored-By: Alan Hayward Co-Authored-By: David Sherwood From-SVN: r242477 --- gcc/ChangeLog | 8 ++++++++ gcc/expr.c | 15 +++++++++------ 2 files changed, 17 insertions(+), 6 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index fe1d9c3b257..a9263afaef2 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2016-11-16 Richard Sandiford + Alan Hayward + David Sherwood + + * expr.c (emit_group_load_1): Tighten check for whether an + access involves only one operand of a CONCAT. Use extract_bit_field + for constants if the bit range does span the whole operand. + 2016-11-16 Richard Sandiford Alan Hayward David Sherwood diff --git a/gcc/expr.c b/gcc/expr.c index 0b0946de345..985c2b3285f 100644 --- a/gcc/expr.c +++ b/gcc/expr.c @@ -2175,19 +2175,22 @@ emit_group_load_1 (rtx *tmps, rtx dst, rtx orig_src, tree type, int ssize) { unsigned int slen = GET_MODE_SIZE (GET_MODE (src)); unsigned int slen0 = GET_MODE_SIZE (GET_MODE (XEXP (src, 0))); + unsigned int elt = bytepos / slen0; + unsigned int subpos = bytepos % slen0; - if ((bytepos == 0 && bytelen == slen0) - || (bytepos != 0 && bytepos + bytelen <= slen)) + if (subpos + bytelen <= slen0) { /* The following assumes that the concatenated objects all have the same size. In this case, a simple calculation can be used to determine the object and the bit field to be extracted. */ - tmps[i] = XEXP (src, bytepos / slen0); - if (! CONSTANT_P (tmps[i]) - && (!REG_P (tmps[i]) || GET_MODE (tmps[i]) != mode)) + tmps[i] = XEXP (src, elt); + if (subpos != 0 + || subpos + bytelen != slen0 + || (!CONSTANT_P (tmps[i]) + && (!REG_P (tmps[i]) || GET_MODE (tmps[i]) != mode))) tmps[i] = extract_bit_field (tmps[i], bytelen * BITS_PER_UNIT, - (bytepos % slen0) * BITS_PER_UNIT, + subpos * BITS_PER_UNIT, 1, NULL_RTX, mode, mode, false); } else -- 2.30.2