https://gcc.gnu.org/g:8804e5b5b127b27d099d0c361fa2161d0b13edef
commit r16-1490-g8804e5b5b127b27d099d0c361fa2161d0b13edef
Author: Jakub Jelinek <ja...@redhat.com>
Date: Thu Jun 12 20:22:39 2025 +0200
recip: Reset range info when replacing sqrt with rsqrt [PR120638]
This pass reuses a SSA_NAME on the lhs of sqrt etc. call as lhs
of .RSQRT etc. call. The following testcase is miscompiled since my recent
ranger cast changes, because we compute (correct) range for sqrtf argument
as well as result but then recip pass keeps using that range for the .RQSRT
call which returns 1. / sqrt, so the function then returns 0.5f
unconditionally.
Note, on foo this is a regression from GCC 15, but on bar it regressed
already with the r14-536 change.
2025-06-12 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/120638
* tree-ssa-math-opts.cc (pass_cse_reciprocals::execute): Call
reset_flow_sensitive_info on arg1.
* gcc.dg/pr120638.c: New test.
Diff:
---
gcc/testsuite/gcc.dg/pr120638.c | 31 +++++++++++++++++++++++++++++++
gcc/tree-ssa-math-opts.cc | 1 +
2 files changed, 32 insertions(+)
diff --git a/gcc/testsuite/gcc.dg/pr120638.c b/gcc/testsuite/gcc.dg/pr120638.c
new file mode 100644
index 000000000000..4a057a028474
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr120638.c
@@ -0,0 +1,31 @@
+/* PR tree-optimization/120638 */
+/* { dg-do run } */
+/* { dg-options "-O2 -ffast-math" } */
+
+extern float sqrtf (float x);
+
+__attribute__((noipa)) float
+foo (unsigned int s)
+{
+ return 0.5f / sqrtf (1.f + s);
+}
+
+__attribute__((noipa)) float
+bar (float s)
+{
+ if (s < 0.0 || s > 65535.0f)
+ __builtin_unreachable ();
+ return 0.5f / sqrtf (1.f + s);
+}
+
+int
+main ()
+{
+ if (__builtin_fabsf (foo (3) - 0.25f) > 0.00390625f
+ || __builtin_fabsf (foo (15) - 0.125f) > 0.00390625f
+ || __builtin_fabsf (foo (63) - 0.0625f) > 0.00390625f
+ || __builtin_fabsf (bar (3.0f) - 0.25f) > 0.00390625f
+ || __builtin_fabsf (bar (15.0f) - 0.125f) > 0.00390625f
+ || __builtin_fabsf (bar (63.0f) - 0.0625f) > 0.00390625f)
+ __builtin_abort ();
+}
diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
index 7e819f37446c..4cfcc420fea5 100644
--- a/gcc/tree-ssa-math-opts.cc
+++ b/gcc/tree-ssa-math-opts.cc
@@ -1053,6 +1053,7 @@ pass_cse_reciprocals::execute (function *fun)
continue;
gimple_replace_ssa_lhs (call, arg1);
+ reset_flow_sensitive_info (arg1);
if (gimple_call_internal_p (call) != (ifn != IFN_LAST))
{
auto_vec<tree, 4> args;
