From 687e30d9d74f5c69a54617147ce3433b07ee59ce Mon Sep 17 00:00:00 2001 From: Eric Botcazou Date: Fri, 17 Sep 2021 10:12:12 +0200 Subject: [PATCH] Fix PR rtl-optimization/102306 This is a duplication of volatile loads introduced during GCC 9 development by the 2->2 mechanism of the RTL combiner. There is already a substantial checking for volatile references in can_combine_p but it implicitly assumes that the combination reduces the number of instructions, which is of course not the case here. So the fix teaches try_combine to abort the combination when it is about to make a copy of volatile references to preserve them. gcc/ PR rtl-optimization/102306 * combine.c (try_combine): Abort the combination if we are about to duplicate volatile references. gcc/testsuite/ * gcc.target/sparc/20210917-1.c: New test. --- gcc/combine.c | 10 ++++++++++ gcc/testsuite/gcc.target/sparc/20210917-1.c | 19 +++++++++++++++++++ 2 files changed, 29 insertions(+) create mode 100644 gcc/testsuite/gcc.target/sparc/20210917-1.c diff --git a/gcc/combine.c b/gcc/combine.c index 290a3667c656..892c834a160a 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -3063,6 +3063,16 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0, return 0; } + /* We cannot safely duplicate volatile references in any case. */ + + if ((added_sets_2 && volatile_refs_p (PATTERN (i2))) + || (added_sets_1 && volatile_refs_p (PATTERN (i1))) + || (added_sets_0 && volatile_refs_p (PATTERN (i0)))) + { + undo_all (); + return 0; + } + /* Count how many auto_inc expressions there were in the original insns; we need to have the same number in the resulting patterns. */ diff --git a/gcc/testsuite/gcc.target/sparc/20210917-1.c b/gcc/testsuite/gcc.target/sparc/20210917-1.c new file mode 100644 index 000000000000..03e8bc58db98 --- /dev/null +++ b/gcc/testsuite/gcc.target/sparc/20210917-1.c @@ -0,0 +1,19 @@ +/* PR rtl-optimization/102306 */ +/* Reported by Daniel Cederman */ + +/* { dg-do compile } */ +/* { dg-require-effective-target ilp32 } */ +/* { dg-options "-O -mcpu=v8" } */ + +extern void foo (void); + +void test (volatile unsigned char *a) +{ + char b = *a; + if (!b) + return; + if (b & 2) + foo (); +} + +/* { dg-final { scan-assembler-times "ldub" 1 } } */ -- 2.47.2