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| author | Andrew Pinski <apinski@marvell.com> | 2023-05-18 22:17:07 +0000 |
|---|---|---|
| committer | Andrew Pinski <apinski@marvell.com> | 2023-06-04 20:48:32 +0000 |
| commit | 6cf856f873c1a2ab39d8fb0a93b5f4505a22feb6 (patch) | |
| tree | a10999e359c049553819ea590c2b0ef22f5d450b /gcc/expr.cc | |
| parent | 908e5ab5c11c64ce92f1aa6e12d571ff5eb9d72a (diff) | |
| download | gcc-6cf856f873c1a2ab39d8fb0a93b5f4505a22feb6.zip gcc-6cf856f873c1a2ab39d8fb0a93b5f4505a22feb6.tar.gz gcc-6cf856f873c1a2ab39d8fb0a93b5f4505a22feb6.tar.bz2 | |
Improve do_store_flag for comparing single bit against that bit
This is a case which I noticed while working on the previous patch.
Sometimes we end up with `a == CST` instead of comparing against 0.
This happens in the following code:
```
unsigned f(unsigned t)
{
if (t & ~(1<<30)) __builtin_unreachable();
t ^= (1<<30);
return t != 0;
}
```
We should handle the case where the nonzero bits is the same as the
comparison operand.
Changes from v1:
* v2: Updated for the bit extraction changes.
OK? Bootstrapped and tested on x86_64-linux-gnu.
gcc/ChangeLog:
* expr.cc (do_store_flag): Improve for single bit testing
not against zero but against that single bit.
Diffstat (limited to 'gcc/expr.cc')
| -rw-r--r-- | gcc/expr.cc | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/gcc/expr.cc b/gcc/expr.cc index 6027e7f..58f5fe7 100644 --- a/gcc/expr.cc +++ b/gcc/expr.cc @@ -13159,12 +13159,15 @@ do_store_flag (sepops ops, rtx target, machine_mode mode) than an scc insn even if we have it. */ if ((code == NE || code == EQ) - && integer_zerop (arg1) + && (integer_zerop (arg1) + || integer_pow2p (arg1)) && (TYPE_PRECISION (ops->type) != 1 || TYPE_UNSIGNED (ops->type))) { wide_int nz = tree_nonzero_bits (arg0); - if (wi::popcount (nz) == 1) + if (wi::popcount (nz) == 1 + && (integer_zerop (arg1) + || wi::to_wide (arg1) == nz)) { tree op0; int bitnum; @@ -13182,7 +13185,9 @@ do_store_flag (sepops ops, rtx target, machine_mode mode) op0 = arg0; bitnum = wi::exact_log2 (nz); } - enum tree_code tcode = code == NE ? NE_EXPR : EQ_EXPR; + enum tree_code tcode = EQ_EXPR; + if ((code == NE) ^ !integer_zerop (arg1)) + tcode = NE_EXPR; type = lang_hooks.types.type_for_mode (mode, unsignedp); return expand_single_bit_test (loc, tcode, |