[gcc/devel/c++-coroutines] Disable some VEC_COND_EXPR transformations after vector lowering

[Iain D Sandoe <iains@gcc.gnu.org>]

https://gcc.gnu.org/g:a1ee6d507b0c26466be519d177f5a08b22f63647

commit a1ee6d507b0c26466be519d177f5a08b22f63647
Author: Marc Glisse <marc.glisse@inria.fr>
Date:   Fri Aug 7 18:49:04 2020 +0200

    Disable some VEC_COND_EXPR transformations after vector lowering
    
    ARM understands VEC_COND_EXPR<v == w, -1, 0> but not a plain v == w which is
    fed to something other than VEC_COND_EXPR (say BIT_IOR_EXPR). This patch avoids
    introducing the second kind of statement after the vector lowering pass, which
    is the last chance to turn v == w back into something the target handles.
    
    This is just a workaround to avoid ICEs, a v == w produced before vector
    lowering will yield pretty bad code. Either the arm target needs to learn to
    handle vector comparisons (aarch64 already does), or the middle-end needs to
    fall back to vcond when plain comparisons are not supported (or ...).
    
    2020-08-07  Marc Glisse  <marc.glisse@inria.fr>
    
            * generic-match-head.c (optimize_vectors_before_lowering_p): New
            function.
            * gimple-match-head.c (optimize_vectors_before_lowering_p):
            Likewise.
            * match.pd ((v ? w : 0) ? a : b, c1 ? c2 ? a : b : b): Use it.

Diff:
---
 gcc/generic-match-head.c | 10 ++++++++++
 gcc/gimple-match-head.c  | 10 ++++++++++
 gcc/match.pd             | 20 +++++++++++---------
 3 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/gcc/generic-match-head.c b/gcc/generic-match-head.c
index 2454baac9d4..fdb528d9686 100644
--- a/gcc/generic-match-head.c
+++ b/gcc/generic-match-head.c
@@ -80,6 +80,16 @@ canonicalize_math_after_vectorization_p ()
   return false;
 }
 
+/* Return true if we can still perform transformations that may introduce
+   vector operations that are not supported by the target. Vector lowering
+   normally handles those, but after that pass, it becomes unsafe.  */
+
+static inline bool
+optimize_vectors_before_lowering_p ()
+{
+  return true;
+}
+
 /* Return true if successive divisions can be optimized.
    Defer to GIMPLE opts.  */
 
diff --git a/gcc/gimple-match-head.c b/gcc/gimple-match-head.c
index 9b3e7298d87..4a65be703b9 100644
--- a/gcc/gimple-match-head.c
+++ b/gcc/gimple-match-head.c
@@ -1158,6 +1158,16 @@ canonicalize_math_after_vectorization_p ()
   return !cfun || (cfun->curr_properties & PROP_gimple_lvec) != 0;
 }
 
+/* Return true if we can still perform transformations that may introduce
+   vector operations that are not supported by the target. Vector lowering
+   normally handles those, but after that pass, it becomes unsafe.  */
+
+static inline bool
+optimize_vectors_before_lowering_p ()
+{
+  return !cfun || (cfun->curr_properties & PROP_gimple_lvec) == 0;
+}
+
 /* Return true if pow(cst, x) should be optimized into exp(log(cst) * x).
    As a workaround for SPEC CPU2017 628.pop2_s, don't do it if arg0
    is an exact integer, arg1 = phi_res +/- cst1 and phi_res = PHI <cst2, ...>
diff --git a/gcc/match.pd b/gcc/match.pd
index d8e3927d3c7..7e5c5a6eae6 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3461,40 +3461,42 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (vec_cond @0 (op! @3 @1) (op! @3 @2))))
 #endif
 
-/* (v ? w : 0) ? a : b is just (v & w) ? a : b  */
+/* (v ? w : 0) ? a : b is just (v & w) ? a : b
+   Currently disabled after pass lvec because ARM understands
+   VEC_COND_EXPR<v==w,-1,0> but not a plain v==w fed to BIT_IOR_EXPR.  */
 (simplify
  (vec_cond (vec_cond:s @0 @3 integer_zerop) @1 @2)
- (if (types_match (@0, @3))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @3))
   (vec_cond (bit_and @0 @3) @1 @2)))
 (simplify
  (vec_cond (vec_cond:s @0 integer_all_onesp @3) @1 @2)
- (if (types_match (@0, @3))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @3))
   (vec_cond (bit_ior @0 @3) @1 @2)))
 (simplify
  (vec_cond (vec_cond:s @0 integer_zerop @3) @1 @2)
- (if (types_match (@0, @3))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @3))
   (vec_cond (bit_ior @0 (bit_not @3)) @2 @1)))
 (simplify
  (vec_cond (vec_cond:s @0 @3 integer_all_onesp) @1 @2)
- (if (types_match (@0, @3))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @3))
   (vec_cond (bit_and @0 (bit_not @3)) @2 @1)))
 
 /* c1 ? c2 ? a : b : b  -->  (c1 & c2) ? a : b  */
 (simplify
  (vec_cond @0 (vec_cond:s @1 @2 @3) @3)
- (if (types_match (@0, @1))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @1))
   (vec_cond (bit_and @0 @1) @2 @3)))
 (simplify
  (vec_cond @0 @2 (vec_cond:s @1 @2 @3))
- (if (types_match (@0, @1))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @1))
   (vec_cond (bit_ior @0 @1) @2 @3)))
 (simplify
  (vec_cond @0 (vec_cond:s @1 @2 @3) @2)
- (if (types_match (@0, @1))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @1))
   (vec_cond (bit_ior (bit_not @0) @1) @2 @3)))
 (simplify
  (vec_cond @0 @3 (vec_cond:s @1 @2 @3))
- (if (types_match (@0, @1))
+ (if (optimize_vectors_before_lowering_p () && types_match (@0, @1))
   (vec_cond (bit_and (bit_not @0) @1) @2 @3)))
 
 /* Simplification moved from fold_cond_expr_with_comparison.  It may also