Hi, The first pass of code generation in the D front-end splits up all compound expressions and discards expressions that have no side effects. This included calls to the `volatileLoad' intrinsic if its result was not used, causing such calls to be eliminated from the program.
We already set TREE_THIS_VOLATILE on the expression, however the tree documentation says if this bit is set in an expression, so is TREE_SIDE_EFFECTS. So set TREE_SIDE_EFFECTS on the expression too. This prevents any early discarding from occuring. Bootstrapped and regression tested on x86_64-linux-gnu/-m32, committed to mainline, and backported to releases/gcc-13, gcc-12, and gcc-11. Regards, Iain. --- PR d/110516 gcc/d/ChangeLog: * intrinsics.cc (expand_volatile_load): Set TREE_SIDE_EFFECTS on the expanded expression. (expand_volatile_store): Likewise. gcc/testsuite/ChangeLog: * gdc.dg/torture/pr110516a.d: New test. * gdc.dg/torture/pr110516b.d: New test. --- gcc/d/intrinsics.cc | 2 ++ gcc/testsuite/gdc.dg/torture/pr110516a.d | 12 ++++++++++++ gcc/testsuite/gdc.dg/torture/pr110516b.d | 12 ++++++++++++ 3 files changed, 26 insertions(+) create mode 100644 gcc/testsuite/gdc.dg/torture/pr110516a.d create mode 100644 gcc/testsuite/gdc.dg/torture/pr110516b.d diff --git a/gcc/d/intrinsics.cc b/gcc/d/intrinsics.cc index 0121d81eb14..aaf04e50baa 100644 --- a/gcc/d/intrinsics.cc +++ b/gcc/d/intrinsics.cc @@ -1007,6 +1007,7 @@ expand_volatile_load (tree callexp) tree type = build_qualified_type (TREE_TYPE (ptrtype), TYPE_QUAL_VOLATILE); tree result = indirect_ref (type, ptr); TREE_THIS_VOLATILE (result) = 1; + TREE_SIDE_EFFECTS (result) = 1; return result; } @@ -1034,6 +1035,7 @@ expand_volatile_store (tree callexp) tree type = build_qualified_type (TREE_TYPE (ptrtype), TYPE_QUAL_VOLATILE); tree result = indirect_ref (type, ptr); TREE_THIS_VOLATILE (result) = 1; + TREE_SIDE_EFFECTS (result) = 1; /* (*(volatile T *) ptr) = value; */ tree value = CALL_EXPR_ARG (callexp, 1); diff --git a/gcc/testsuite/gdc.dg/torture/pr110516a.d b/gcc/testsuite/gdc.dg/torture/pr110516a.d new file mode 100644 index 00000000000..276455ae408 --- /dev/null +++ b/gcc/testsuite/gdc.dg/torture/pr110516a.d @@ -0,0 +1,12 @@ +// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110516 +// { dg-do compile } +// { dg-options "-fno-moduleinfo -fdump-tree-optimized" } +void fn110516(ubyte* ptr) +{ + import core.volatile : volatileLoad; + volatileLoad(ptr); + volatileLoad(ptr); + volatileLoad(ptr); + volatileLoad(ptr); +} +// { dg-final { scan-tree-dump-times " ={v} " 4 "optimized" } } diff --git a/gcc/testsuite/gdc.dg/torture/pr110516b.d b/gcc/testsuite/gdc.dg/torture/pr110516b.d new file mode 100644 index 00000000000..b7a67e716a5 --- /dev/null +++ b/gcc/testsuite/gdc.dg/torture/pr110516b.d @@ -0,0 +1,12 @@ +// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110516 +// { dg-do compile } +// { dg-options "-fno-moduleinfo -fdump-tree-optimized" } +void fn110516(ubyte* ptr) +{ + import core.volatile : volatileStore; + volatileStore(ptr, 0); + volatileStore(ptr, 0); + volatileStore(ptr, 0); + volatileStore(ptr, 0); +} +// { dg-final { scan-tree-dump-times " ={v} " 4 "optimized" } } -- 2.39.2