In this case we are not removing convert to a bigger size
back to the same size (or smaller) if signedness does not
match.
For an example:
```
signed char _1;
...
_1 = *a_4(D);
b_5 = (short unsigned int) _1;
_2 = (unsigned char) b_5;
```
The inner cast is not needed and can be removed but was not.
The match pattern for removing the extra cast is overly
complex so decided to add a new case for rather than trying
to modify the current if statement here.
Committed as approved. Bootstrapped and tested on x86_64-linux-gnu with no
regressions.
gcc/ChangeLog:
* match.pd (nested int casts): A truncation (to the same size or
smaller)
can always remove the inner cast.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/cast-1.c: New test.
* gcc.dg/tree-ssa/cast-2.c: New test.
---
gcc/match.pd | 10 ++++++++++
gcc/testsuite/gcc.dg/tree-ssa/cast-1.c | 12 ++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/cast-2.c | 12 ++++++++++++
3 files changed, 34 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cast-1.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cast-2.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 74f0a84f31d..cfd6ea08807 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4340,6 +4340,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
&& ! (final_ptr && inside_prec != inter_prec))
(ocvt @0))
+ /* `(outer:M)(inter:N) a:O`
+ can be converted to `(outer:M) a`
+ if M <= O && N >= O. No matter what signedness of the casts,
+ as the final is either a truncation from the original or just
+ a sign change of the type. */
+ (if (inside_int && inter_int && final_int
+ && final_prec <= inside_prec
+ && inter_prec >= inside_prec)
+ (convert @0))
+
/* A truncation to an unsigned type (a zero-extension) should be
canonicalized as bitwise and of a mask. */
(if (GIMPLE /* PR70366: doing this in GENERIC breaks -Wconversion. */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cast-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/cast-1.c
new file mode 100644
index 00000000000..0f33ab58b3e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/cast-1.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+
+
+void f(signed char *a, unsigned char *c)
+{
+ unsigned short b = *a;
+ *c = ((unsigned char)b);
+}
+
+
+/* { dg-final { scan-tree-dump-not "\\(short unsigned int\\)" "optimized"} } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cast-2.c
b/gcc/testsuite/gcc.dg/tree-ssa/cast-2.c
new file mode 100644
index 00000000000..d665e924831
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/cast-2.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+
+
+void f(signed short *a, unsigned char *c)
+{
+ unsigned long b = *a;
+ *c = ((unsigned char)b);
+}
+
+
+/* { dg-final { scan-tree-dump-not "\\(long unsigned int\\)" "optimized"} } */
--
2.31.1
