The following fixes MIN/MAX recognition for comparisons that
we turned into equality compares (for tests like unsigned < 1).
It turns out we don't do a very good job in expanding them,
nevertheless this GIMPLE level fix is good and we get slight
improvements in code generation.
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
Richard.
>From 0b801cf0ed81d8bd0945e68196efc7d1fc676562 Mon Sep 17 00:00:00 2001
From: Richard Guenther <rguent...@suse.de>
Date: Wed, 7 Nov 2018 16:20:54 +0100
Subject: [PATCH] fix-pr87913
PR tree-optimization/87913
* tree-ssa-phiopt.c (minmax_replacement): Turn EQ/NE compares
of extreme values to ordered comparisons.
* gcc.dg/tree-ssa/phi-opt-20.c: New testcase.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-20.c
b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-20.c
new file mode 100644
index 00000000000..c310308e3a6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-20.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-phiopt1" } */
+
+unsigned int f(unsigned int num)
+{
+ return num < 1 ? 1 : num;
+}
+
+unsigned int g(unsigned int num)
+{
+ return num > (unsigned)__INT_MAX__ * 2 ? (unsigned)__INT_MAX__ * 2 : num;
+}
+
+int h(int num)
+{
+ return num < -__INT_MAX__ ? -__INT_MAX__ : num;
+}
+
+int i(int num)
+{
+ return num > __INT_MAX__-1 ? __INT_MAX__-1 : num;
+}
+
+/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "phiopt1" } } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "phiopt1" } } */
diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
index 07845101b86..64039e2484e 100644
--- a/gcc/tree-ssa-phiopt.c
+++ b/gcc/tree-ssa-phiopt.c
@@ -1204,7 +1204,7 @@ minmax_replacement (basic_block cond_bb, basic_block
middle_bb,
edge e0, edge e1, gimple *phi,
tree arg0, tree arg1)
{
- tree result, type;
+ tree result, type, rhs;
gcond *cond;
gassign *new_stmt;
edge true_edge, false_edge;
@@ -1220,6 +1220,25 @@ minmax_replacement (basic_block cond_bb, basic_block
middle_bb,
cond = as_a <gcond *> (last_stmt (cond_bb));
cmp = gimple_cond_code (cond);
+ rhs = gimple_cond_rhs (cond);
+
+ /* Turn EQ/NE of extreme values to order comparisons. */
+ if ((cmp == NE_EXPR || cmp == EQ_EXPR)
+ && TREE_CODE (rhs) == INTEGER_CST)
+ {
+ if (wi::eq_p (wi::to_wide (rhs), wi::min_value (TREE_TYPE (rhs))))
+ {
+ cmp = (cmp == EQ_EXPR) ? LT_EXPR : GE_EXPR;
+ rhs = wide_int_to_tree (TREE_TYPE (rhs),
+ wi::min_value (TREE_TYPE (rhs)) + 1);
+ }
+ else if (wi::eq_p (wi::to_wide (rhs), wi::max_value (TREE_TYPE (rhs))))
+ {
+ cmp = (cmp == EQ_EXPR) ? GT_EXPR : LE_EXPR;
+ rhs = wide_int_to_tree (TREE_TYPE (rhs),
+ wi::max_value (TREE_TYPE (rhs)) - 1);
+ }
+ }
/* This transformation is only valid for order comparisons. Record which
operand is smaller/larger if the result of the comparison is true. */
@@ -1228,7 +1247,7 @@ minmax_replacement (basic_block cond_bb, basic_block
middle_bb,
if (cmp == LT_EXPR || cmp == LE_EXPR)
{
smaller = gimple_cond_lhs (cond);
- larger = gimple_cond_rhs (cond);
+ larger = rhs;
/* If we have smaller < CST it is equivalent to smaller <= CST-1.
Likewise smaller <= CST is equivalent to smaller < CST+1. */
if (TREE_CODE (larger) == INTEGER_CST)
@@ -1255,7 +1274,7 @@ minmax_replacement (basic_block cond_bb, basic_block
middle_bb,
}
else if (cmp == GT_EXPR || cmp == GE_EXPR)
{
- smaller = gimple_cond_rhs (cond);
+ smaller = rhs;
larger = gimple_cond_lhs (cond);
/* If we have larger > CST it is equivalent to larger >= CST+1.
Likewise larger >= CST is equivalent to larger > CST-1. */
