On 2/3/22 15:33, Jakub Jelinek wrote:
On Thu, Feb 03, 2022 at 03:07:03PM -0500, Jason Merrill wrote:
--- gcc/fold-const.h.jj 2022-02-01 20:10:51.235856007 +0100
+++ gcc/fold-const.h 2022-02-03 15:02:02.700228631 +0100
-/* Non-zero if we are folding constants inside an initializer; zero
- otherwise. */
+/* Nonzero if we are folding constants inside an initializer or a C++
+ manifestly-constant-evaluated context; zero otherwise.
+ Should be used when folding in initializer enables additional
+ optimizations. */
extern int folding_initializer;
+/* Nonzer of we are folding C++ manifestly-constant-evaluated context; zero
"Nonzero if"
Oops, thanks for catching it.
+ if (!folding_cxx_constexpr
+ && ((DECL_P (base0) && TREE_CODE (base1) == STRING_CST)
+ || (TREE_CODE (base0) == STRING_CST && DECL_P (base1))
+ || (TREE_CODE (base0) == STRING_CST
+ && TREE_CODE (base1) == STRING_CST
+ && ioff0 >= 0 && ioff1 >= 0
+ && ioff0 < TREE_STRING_LENGTH (base0)
+ && ioff1 < TREE_STRING_LENGTH (base1)
+ /* This is a too conservative test that the STRING_CSTs
+ will not end up being string-merged. */
+ && strncmp (TREE_STRING_POINTER (base0) + ioff0,
+ TREE_STRING_POINTER (base1) + ioff1,
+ MIN (TREE_STRING_LENGTH (base0) - ioff0,
+ TREE_STRING_LENGTH (base1) - ioff1)) != 0)))
;
- else if (!DECL_P (base0) || !DECL_P (base1))
+ /* Punt on non-zero offsets from functions. */
+ else if ((TREE_CODE (base0) == FUNCTION_DECL && ioff0)
+ || (TREE_CODE (base1) == FUNCTION_DECL && ioff1))
+ return 2;
+ else if ((!DECL_P (base0)
+ && (!folding_cxx_constexpr || TREE_CODE (base0) != STRING_CST))
+ || (!DECL_P (base1)
+ && (!folding_cxx_constexpr || TREE_CODE (base1) != STRING_CST)))
I think it would be clearer to leave the !DECL_P case alone and add
/* In C++ it is unspecified, and so non-constant, whether two
equivalent strings have the same address. */
else if (folding_cxx_constexpr
&& (TREE_CODE (base0) == STRING_CST
|| TREE_CODE (base1) == STRING_CST)
The point was to let the first if handle for
!folding_cxx_constexpr the cases with STRING_CST
as one or both operands and if that falls through, return 2.
Ah, I see. And then for folding_cxx_constexpr you have your new code
toward the bottom of the function that can say they're unequal in some
cases. Can you combine the STRING_CST handling for both values of
folding_cxx_constexpr instead of having them so far apart?
Jason
