[PATCH] tree-optimization/102008 - restore if-conversion of adjacent loads

Richard Biener rguenther@suse.de
Wed Mar 16 12:42:26 GMT 2022


The following re-orders the newly added code sinking pass before
the last phiopt pass which performs hoisting of adjacent loads
with the intent to enable if-conversion on those.

I've added the aarch64 specific testcase from the PR.

Bootstrapped and tested on x86_64-unknown-linux-gnu, verified
the testcase fails/passes with a aarch64 cross.

OK?

Thanks,
Richard.

2022-03-16  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102008
	* passes.def: Move the added code sinking pass before the
	preceeding phiopt pass.

	* gcc.target/aarch64/pr102008.c: New testcase.
---
 gcc/passes.def                              |  2 +-
 gcc/testsuite/gcc.target/aarch64/pr102008.c | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/aarch64/pr102008.c

diff --git a/gcc/passes.def b/gcc/passes.def
index f7718181038..c8903b4ec16 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -349,10 +349,10 @@ along with GCC; see the file COPYING3.  If not see
       /* After late CD DCE we rewrite no longer addressed locals into SSA
 	 form if possible.  */
       NEXT_PASS (pass_forwprop);
+      NEXT_PASS (pass_sink_code);
       NEXT_PASS (pass_phiopt, false /* early_p */);
       NEXT_PASS (pass_fold_builtins);
       NEXT_PASS (pass_optimize_widening_mul);
-      NEXT_PASS (pass_sink_code);
       NEXT_PASS (pass_store_merging);
       NEXT_PASS (pass_tail_calls);
       /* If DCE is not run before checking for uninitialized uses,
diff --git a/gcc/testsuite/gcc.target/aarch64/pr102008.c b/gcc/testsuite/gcc.target/aarch64/pr102008.c
new file mode 100644
index 00000000000..d54436c0ffd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/pr102008.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+struct Foo {  int a;  int b; };
+
+int test(int side, const struct Foo *foo) {
+  if (side == 1) return foo->a;
+  return foo->b;
+}
+
+/* We want to if-convert the load, not the address.  */
+/* { dg-final { scan-assembler-not "add" } } */
+/* { dg-final { scan-assembler-times "csel" 1 } } */
-- 
2.34.1


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