From: Robin Dapp <rdapp@ventanamicro.com>
Date: Fri, 1 Dec 2023 08:45:29 +0000 (+0100)
Subject: RISC-V: Fix rawmemchr implementation.
X-Git-Tag: basepoints/gcc-15~4017
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cdb34bf5dd10df967b7f72a502a48cc34e284ef0;p=thirdparty%2Fgcc.git

RISC-V: Fix rawmemchr implementation.

This fixes a bug in the rawmemchr implementation by incrementing the
source address by vl * element_size instead of just vl.

This is normally harmless as we will just scan the same region more than
once but, in combination with an older qemu version, will lead to
an execution failure in SPEC2017.

gcc/ChangeLog:

	* config/riscv/riscv-string.cc (expand_rawmemchr): Increment
	source address by vl * element_size.
---

diff --git a/gcc/config/riscv/riscv-string.cc b/gcc/config/riscv/riscv-string.cc
index f3a4d3ddd47f..594ff49fc5ac 100644
--- a/gcc/config/riscv/riscv-string.cc
+++ b/gcc/config/riscv/riscv-string.cc
@@ -1017,6 +1017,8 @@ expand_rawmemchr (machine_mode mode, rtx dst, rtx src, rtx pat)
   machine_mode mask_mode = riscv_vector::get_mask_mode (vmode);
 
   rtx cnt = gen_reg_rtx (Pmode);
+  emit_move_insn (cnt, CONST0_RTX (Pmode));
+
   rtx end = gen_reg_rtx (Pmode);
   rtx vec = gen_reg_rtx (vmode);
   rtx mask = gen_reg_rtx (mask_mode);
@@ -1033,6 +1035,11 @@ expand_rawmemchr (machine_mode mode, rtx dst, rtx src, rtx pat)
 
   rtx vsrc = change_address (src, vmode, src_addr);
 
+  /* Bump the pointer.  */
+  rtx step = gen_reg_rtx (Pmode);
+  emit_insn (gen_rtx_SET (step, gen_rtx_ASHIFT (Pmode, cnt, GEN_INT (shift))));
+  emit_insn (gen_rtx_SET (src_addr, gen_rtx_PLUS (Pmode, src_addr, step)));
+
   /* Emit a first-fault load.  */
   rtx vlops[] = {vec, vsrc};
   emit_vlmax_insn (code_for_pred_fault_load (vmode),
@@ -1055,16 +1062,10 @@ expand_rawmemchr (machine_mode mode, rtx dst, rtx src, rtx pat)
   emit_nonvlmax_insn (code_for_pred_ffs (mask_mode, Pmode),
 		      riscv_vector::CPOP_OP, vfops, cnt);
 
-  /* Bump the pointer.  */
-  emit_insn (gen_rtx_SET (src_addr, gen_rtx_PLUS (Pmode, src_addr, cnt)));
-
   /* Emit the loop condition.  */
   rtx test = gen_rtx_LT (VOIDmode, end, const0_rtx);
   emit_jump_insn (gen_cbranch4 (Pmode, test, end, const0_rtx, loop));
 
-  /*  We overran by CNT, subtract it.  */
-  emit_insn (gen_rtx_SET (src_addr, gen_rtx_MINUS (Pmode, src_addr, cnt)));
-
   /*  We found something at SRC + END * [1,2,4,8].  */
   emit_insn (gen_rtx_SET (end, gen_rtx_ASHIFT (Pmode, end, GEN_INT (shift))));
   emit_insn (gen_rtx_SET (dst, gen_rtx_PLUS (Pmode, src_addr, end)));