i386: Use a new temp slot kind for splitter to floatdi<mode>2_i387_with_xmm [PR104674]

As mentioned in the PR, the following testcase is miscompiled for similar
reasons as the already fixed PR78791 - we use SLOT_TEMP slots in various
places during expansion and during expansion we can guarantee that the
lifetime of those temporary slot doesn't overlap.  But the following
splitter uses SLOT_TEMP too and in between expansion and split1 there is
a possibility that something extends the lifetime of SLOT_TEMP created
slots across an instruction that will be split by this splitter.

The following patch fixes it by using a new temp slot kind to make sure
it doesn't reuse a SLOT_TEMP that could be live across the instruction.

2022-02-25  Jakub Jelinek  <jakub@redhat.com>

	PR target/104674
	* config/i386/i386.h (enum ix86_stack_slot): Add SLOT_FLOATxFDI_387.
	* config/i386/i386.md (splitter to floatdi<mode>2_i387_with_xmm): Use
	SLOT_FLOATxFDI_387 rather than SLOT_TEMP.

	* gcc.target/i386/pr104674.c: New test.

diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index f41e090..b37d4a9 100644 (file)
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -2414,6 +2414,7 @@ enum ix86_stack_slot
   SLOT_CW_FLOOR,
   SLOT_CW_CEIL,
   SLOT_STV_TEMP,
+  SLOT_FLOATxFDI_387,
   MAX_386_STACK_LOCALS
 };
 

diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 8ffa641..e7c5490 100644 (file)
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -5412,9 +5412,8 @@
    && can_create_pseudo_p ()"
   [(const_int 0)]
 {
-  emit_insn (gen_floatdi<mode>2_i387_with_xmm
-            (operands[0], operands[1],
-             assign_386_stack_local (DImode, SLOT_TEMP)));
+  rtx s = assign_386_stack_local (DImode, SLOT_FLOATxFDI_387);
+  emit_insn (gen_floatdi<mode>2_i387_with_xmm (operands[0], operands[1], s));
   DONE;
 })
 

diff --git a/gcc/testsuite/gcc.target/i386/pr104674.c b/gcc/testsuite/gcc.target/i386/pr104674.c
new file mode 100644 (file)
index 0000000..c8f3e9b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr104674.c
@@ -0,0 +1,31 @@
+/* PR target/104674 */
+/* { dg-do run { target sse2_runtime } } */
+/* { dg-options "-O2 -msse2 -mfpmath=sse" } */
+
+__attribute__((noipa)) double
+bar (double x, double y)
+{
+  return x + y;
+}
+
+__attribute__((noipa)) double
+foo (long long x)
+{
+  long long a = x / 10000000;
+  int b = x % 10000000;
+  double s = (double) a;
+  double n = (double) b / 1e7;
+  double t = s + n;
+  if (t == s + 1.0)
+    t = bar (t, s);
+  return t;
+}
+
+int
+main ()
+{
+  long long n = 888888;
+  n = n * 10000000;
+  if (foo (n) != 888888.0)
+    __builtin_abort ();
+}