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| author | Richard Biener <rguenther@suse.de> | 2020-08-26 08:44:59 +0200 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2020-08-27 08:07:34 +0200 |
| commit | 989bc4ca2f2978baecff00f6d0532994b82897ef (patch) | |
| tree | 818b5867caed131fd5c269b18d5a1948d6cbb459 /gcc | |
| parent | 3ae0cd94abc15e33dc06ca7a5f76f14b1d74129f (diff) | |
| download | gcc-989bc4ca2f2978baecff00f6d0532994b82897ef.zip gcc-989bc4ca2f2978baecff00f6d0532994b82897ef.tar.gz gcc-989bc4ca2f2978baecff00f6d0532994b82897ef.tar.bz2 | |
tree-optimization/96565 - improve DSE with paths ending in noreturn
This improves DSEs stmt walking by not considering a DEF without
uses for further processing (and thus giving up when there's two
paths to follow).
2020-08-26 Richard Biener <rguenther@suse.de>
PR tree-optimization/96565
* tree-ssa-dse.c (dse_classify_store): Remove defs with
no uses from further processing.
* gcc.dg/tree-ssa/ssa-dse-40.c: New testcase.
* gcc.dg/builtin-object-size-4.c: Adjust.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/testsuite/gcc.dg/builtin-object-size-4.c | 3 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-40.c | 16 | ||||
| -rw-r--r-- | gcc/tree-ssa-dse.c | 11 |
3 files changed, 30 insertions, 0 deletions
diff --git a/gcc/testsuite/gcc.dg/builtin-object-size-4.c b/gcc/testsuite/gcc.dg/builtin-object-size-4.c index c22654d..9f159e3 100644 --- a/gcc/testsuite/gcc.dg/builtin-object-size-4.c +++ b/gcc/testsuite/gcc.dg/builtin-object-size-4.c @@ -170,6 +170,9 @@ test1 (void *q, int x) r = (char *) L"abcd\0efg"; if (__builtin_object_size (r + 2, 3) != sizeof (L"abcd\0efg") - 2) abort (); + /* Prevent DSE from removing calls that prevent bad combining of + addresses and offsets. */ + asm volatile ("" : : "g" (&a)); } size_t l1 = 1; diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-40.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-40.c new file mode 100644 index 0000000..36f69c0 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-40.c @@ -0,0 +1,16 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-dse1-details" } */ + +_Bool g(void); + +void f(int x) +{ + char arr[x]; + + arr[0] = 0; + + if (g()) + __builtin_abort(); +} + +/* { dg-final { scan-tree-dump "Deleted dead store" "dse1" } } */ diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c index cc93f55..76eed06 100644 --- a/gcc/tree-ssa-dse.c +++ b/gcc/tree-ssa-dse.c @@ -898,6 +898,17 @@ dse_classify_store (ao_ref *ref, gimple *stmt, *by_clobber_p = false; defs.unordered_remove (i); } + /* If the path ends here we do not need to process it further. + This for example happens with calls to noreturn functions. */ + else if (gimple_code (def) != GIMPLE_PHI + && has_zero_uses (gimple_vdef (def))) + { + /* But if the store is to global memory it is definitely + not dead. */ + if (ref_may_alias_global_p (ref)) + return DSE_STORE_LIVE; + defs.unordered_remove (i); + } /* In addition to kills we can remove defs whose only use is another def in defs. That can only ever be PHIs of which we track a single for simplicity reasons (we fail for multiple |