From 4c3792d448964f7bd99e7eac2c29c9eb7c2bfb84 Mon Sep 17 00:00:00 2001 From: Iain Sandoe Date: Mon, 7 Feb 2022 15:36:35 +0000 Subject: [PATCH] LRA, rs6000, Darwin: Amend lo_sum use for forced constants [PR104117]. Two issues resulted in this PR, which manifests when we force a constant into memory in LRA (in PIC code on Darwin). The presence of such forced constants is quite dependent on other RTL optimisations, and it is easy for the issue to become latent for a specific case. First, in the Darwin-specific rs6000 backend code, we were not being careful enough in rejecting invalid symbolic addresses. Specifically, when generating PIC code, we require a SYMBOL_REF to be wrapped in an UNSPEC_MACHOPIC_OFFSET. Second, LRA was attempting to load a register using an invalid lo_sum address. Signed-off-by: Iain Sandoe Co-authored-by: Vladimir Makarov PR target/104117 gcc/ChangeLog: * config/rs6000/rs6000.cc (darwin_rs6000_legitimate_lo_sum_const_p): Check for UNSPEC_MACHOPIC_OFFSET wrappers on symbolic addresses when emitting PIC code. (legitimate_lo_sum_address_p): Likewise. * lra-constraints.cc (process_address_1): Do not attempt to emit a reg load from an invalid lo_sum address. --- gcc/config/rs6000/rs6000.cc | 38 ++++++++++++++++++++++++++++++++++++-- gcc/lra-constraints.cc | 17 ++--------------- 2 files changed, 38 insertions(+), 17 deletions(-) diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc index eaba9a2..bc3ef072 100644 --- a/gcc/config/rs6000/rs6000.cc +++ b/gcc/config/rs6000/rs6000.cc @@ -8317,8 +8317,14 @@ darwin_rs6000_legitimate_lo_sum_const_p (rtx x, machine_mode mode) if (GET_CODE (x) == CONST) x = XEXP (x, 0); + /* If we are building PIC code, then any symbol must be wrapped in an + UNSPEC_MACHOPIC_OFFSET so that it will get the picbase subtracted. */ + bool machopic_offs_p = false; if (GET_CODE (x) == UNSPEC && XINT (x, 1) == UNSPEC_MACHOPIC_OFFSET) - x = XVECEXP (x, 0, 0); + { + x = XVECEXP (x, 0, 0); + machopic_offs_p = true; + } rtx sym = NULL_RTX; unsigned HOST_WIDE_INT offset = 0; @@ -8349,6 +8355,9 @@ darwin_rs6000_legitimate_lo_sum_const_p (rtx x, machine_mode mode) if (sym) { tree decl = SYMBOL_REF_DECL (sym); + /* As noted above, PIC code cannot use a bare SYMBOL_REF. */ + if (TARGET_MACHO && flag_pic && !machopic_offs_p) + return false; #if TARGET_MACHO if (MACHO_SYMBOL_INDIRECTION_P (sym)) /* The decl in an indirection symbol is the original one, which might @@ -8936,7 +8945,7 @@ legitimate_lo_sum_address_p (machine_mode mode, rtx x, int strict) return false; x = XEXP (x, 1); - if (TARGET_ELF || TARGET_MACHO) + if (TARGET_ELF) { bool large_toc_ok; @@ -8962,7 +8971,32 @@ legitimate_lo_sum_address_p (machine_mode mode, rtx x, int strict) return CONSTANT_P (x) || large_toc_ok; } + else if (TARGET_MACHO) + { + if (GET_MODE_NUNITS (mode) != 1) + return false; + if (GET_MODE_SIZE (mode) > UNITS_PER_WORD + && !(/* see above */ + TARGET_HARD_FLOAT && (mode == DFmode || mode == DDmode))) + return false; +#if TARGET_MACHO + if (MACHO_DYNAMIC_NO_PIC_P || !flag_pic) + return CONSTANT_P (x); +#endif + /* Macho-O PIC code from here. */ + if (GET_CODE (x) == CONST) + x = XEXP (x, 0); + + /* SYMBOL_REFs need to be wrapped in an UNSPEC_MACHOPIC_OFFSET. */ + if (SYMBOL_REF_P (x)) + return false; + /* So this is OK if the wrapped object is const. */ + if (GET_CODE (x) == UNSPEC + && XINT (x, 1) == UNSPEC_MACHOPIC_OFFSET) + return CONSTANT_P (XVECEXP (x, 0, 0)); + return CONSTANT_P (x); + } return false; } diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc index fdff9e0..c700c3f 100644 --- a/gcc/lra-constraints.cc +++ b/gcc/lra-constraints.cc @@ -3625,21 +3625,8 @@ process_address_1 (int nop, bool check_only_p, *ad.inner = gen_rtx_LO_SUM (Pmode, new_reg, addr); if (!valid_address_p (op, &ad, cn)) { - /* Try to put lo_sum into register. */ - insn = emit_insn (gen_rtx_SET - (new_reg, - gen_rtx_LO_SUM (Pmode, new_reg, addr))); - code = recog_memoized (insn); - if (code >= 0) - { - *ad.inner = new_reg; - if (!valid_address_p (op, &ad, cn)) - { - *ad.inner = addr; - code = -1; - } - } - + *ad.inner = addr; /* Punt. */ + code = -1; } } if (code < 0) -- 2.7.4