| Message ID | 006001d80ed7$710cc750$532655f0$@nextmovesoftware.com |
|---|---|
| State | New |
| Headers | show |
| Series | PR middle-end/104140: bootstrap ICE on riscv. | expand |
> Am 21.01.2022 um 15:59 schrieb Roger Sayle <roger@nextmovesoftware.com>: > > > > This patch resolves the P1 "ice-on-valid-code" regression boostrapping > > GCC on risv-unknown-linux-gnu caused by my recent MULT_HIGHPART_EXPR > > functionality. RISC-V differs from x86_64 and many targets by > > supporting a usmusidi3 instruction, basically a widening multiply > > where one operand is signed and the other is unsigned. Alas the > > final version of my patch to recognize MULT_HIGHPART_EXPR didn't > > sufficiently defend against the operands of WIDEN_MULT_EXPR having > > different signedness. This is fixed by the two-line change to > > tree-ssa-math-opts.c's convert_mult_to_highpart in the patch below. > > > > The majority of the rest of the patch is to the documentation > > (in tree.def and generic.texi). It turns out that WIDEN_MULT_EXPR > > wasn't previously documented in generic.texi, let alone the slightly > > unusual semantics of allowing mismatched (signed vs unsigned) operands. > > This also clarifies that MULT_HIGHPART_EXPR currently requires the > > signedness of operands to match [but this might change in future > > release of GCC to support targets with usmul<mode>3_highpart. > > > > The one final chunk of this patch (that is hopefully sufficiently > > close to obvious for stage 4) is a similar (NULL pointer) sanity > > check in riscv_cpu_cpp_builtins. Currently running cc1 from the > > command line (or from gdb) without specifying -march results in a > > segmentation fault (ICE). This is a minor annoyance tracking down > > issues (in cross compilers) for riscv, and trivially fixed as below. > > > > > > This patch has been tested both on x86_64-pc-linux-gnu with a full > > make bootstrap and make -k check, and on a cross-compiler to > > riscv-unknown-linux-gnu where I was able to confirm the new test > > case now passes. Ok for mainline? Ok. Thanks, Richard > > > > > 2022-01-22 Roger Sayle <roger@nextmovesoftware.com> > > > > gcc/ChangeLog > > * tree-ssa-math-opts.c (convert_mult_to_highpart): Check that the > > operands of the widening multiplication are either both signed or > > both unsigned, and abort the conversion if mismatched. > > * doc/generic.texi (WIDEN_MULT_EXPR): Describe expression node. > > (MULT_HIGHPART_EXPR): Clarify that operands must have the same > > signedness. > > * tree.def (MULT_HIGHPART_EXPR): Document both operands must have > > integer types with the same precision and signedness. > > (WIDEN_MULT_EXPR): Document that operands must have integer types > > with the same precision, but possibly differing signedness. > > * config/riscv/risc-v.c (riscv_cpu_cpp_builtins): Defend against > > riscv_current_subset_list returning a NULL pointer (empty list). > > > > gcc/testsuite/ChangeLog > > * gcc.target/riscv/pr104140.c: New test case. > > > > > > Thanks in advance (and sorry for the inconvenience). > > Roger > > -- > > > > > > <patch.txt>
diff --git a/gcc/config/riscv/riscv-c.c b/gcc/config/riscv/riscv-c.c index 211472f..73c62f4 100644 --- a/gcc/config/riscv/riscv-c.c +++ b/gcc/config/riscv/riscv-c.c @@ -108,6 +108,9 @@ riscv_cpu_cpp_builtins (cpp_reader *pfile) builtin_define_with_int_value ("__riscv_arch_test", 1); const riscv_subset_list *subset_list = riscv_current_subset_list (); + if (!subset_list) + return; + size_t max_ext_len = 0; /* Figure out the max length of extension name for reserving buffer. */ diff --git a/gcc/doc/generic.texi b/gcc/doc/generic.texi index bb07775..bf27a0e 100644 --- a/gcc/doc/generic.texi +++ b/gcc/doc/generic.texi @@ -1318,6 +1318,7 @@ The type of the node specifies the alignment of the access. @tindex PLUS_EXPR @tindex MINUS_EXPR @tindex MULT_EXPR +@tindex WIDEN_MULT_EXPR @tindex MULT_HIGHPART_EXPR @tindex RDIV_EXPR @tindex TRUNC_DIV_EXPR @@ -1532,10 +1533,18 @@ one operand is of floating type and the other is of integral type. The behavior of these operations on signed arithmetic overflow is controlled by the @code{flag_wrapv} and @code{flag_trapv} variables. +@item WIDEN_MULT_EXPR +This node represents a widening multiplication. The operands have +integral types with same @var{b} bits of precision, producing an +integral type result with at least @math{2@var{b}} bits of precision. +The behaviour is equivalent to extending both operands, possibly of +different signedness, to the result type, then multiplying them. + @item MULT_HIGHPART_EXPR This node represents the ``high-part'' of a widening multiplication. For an integral type with @var{b} bits of precision, the result is the most significant @var{b} bits of the full @math{2@var{b}} product. +Both operands must have the same precision and same signedness. @item RDIV_EXPR This node represents a floating point division operation. diff --git a/gcc/testsuite/gcc.target/riscv/pr104140.c b/gcc/testsuite/gcc.target/riscv/pr104140.c new file mode 100644 index 0000000..648e131 --- /dev/null +++ b/gcc/testsuite/gcc.target/riscv/pr104140.c @@ -0,0 +1,11 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -march=rv32im -mabi=ilp32" } */ +int x; +unsigned u, v; +void f (void) +{ + long long y = x; + u = y * v >> 32; +} +void g (void) { f (); } + diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c index 1b6a57b..28ed116 100644 --- a/gcc/tree-ssa-math-opts.c +++ b/gcc/tree-ssa-math-opts.c @@ -4608,6 +4608,10 @@ convert_mult_to_highpart (gassign *stmt, gimple_stmt_iterator *gsi) if (bits < prec || bits >= 2 * prec) return false; + /* For the time being, require operands to have the same sign. */ + if (unsignedp != TYPE_UNSIGNED (TREE_TYPE (mop2))) + return false; + machine_mode mode = TYPE_MODE (optype); optab tab = unsignedp ? umul_highpart_optab : smul_highpart_optab; if (optab_handler (tab, mode) == CODE_FOR_nothing) diff --git a/gcc/tree.def b/gcc/tree.def index 36b91f0..0aece802 100644 --- a/gcc/tree.def +++ b/gcc/tree.def @@ -700,7 +700,9 @@ DEFTREECODE (POINTER_PLUS_EXPR, "pointer_plus_expr", tcc_binary, 2) DEFTREECODE (POINTER_DIFF_EXPR, "pointer_diff_expr", tcc_binary, 2) /* Highpart multiplication. For an integral type with precision B, - returns bits [2B-1, B] of the full 2*B product. */ + returns bits [2B-1, B] of the full 2*B product. Both operands + and the result should have integer types of the same precision + and signedness. */ DEFTREECODE (MULT_HIGHPART_EXPR, "mult_highpart_expr", tcc_binary, 2) /* Division for integer result that rounds the quotient toward zero. */ @@ -1349,10 +1351,12 @@ DEFTREECODE (WIDEN_SUM_EXPR, "widen_sum_expr", tcc_binary, 2) DEFTREECODE (SAD_EXPR, "sad_expr", tcc_expression, 3) /* Widening multiplication. - The two arguments are of type t1. - The result is of type t2, such that t2 is at least twice - the size of t1. WIDEN_MULT_EXPR is equivalent to first widening (promoting) - the arguments from type t1 to type t2, and then multiplying them. */ + The two arguments are of type t1 and t2, both integral types that + have the same precision, but possibly different signedness. + The result is of integral type t3, such that t3 is at least twice + the size of t1/t2. WIDEN_MULT_EXPR is equivalent to first widening + (promoting) the arguments from type t1 to type t3, and from t2 to + type t3 and then multiplying them. */ DEFTREECODE (WIDEN_MULT_EXPR, "widen_mult_expr", tcc_binary, 2) /* Widening multiply-accumulate.