The following makes sure that FP x > y ? x : y style max/min operations are if-converted at the GIMPLE level. While we can neither match it to MAX_EXPR nor .FMAX as both have different semantics with IEEE than the ternary ?: operation we can make sure to maintain this form as a COND_EXPR so backends have the chance to match this to instructions their ISA offers.
The patch does this in phiopt where we recognize min/max and instead of giving up when we have to honor NaNs we alter the generated code to a COND_EXPR. This resolves PR88540 and we can then SLP vectorize the min operation for its testcase. It also resolves part of the regressions observed with the change matching bit-inserts of bit-field-refs to vec_perm. Expansion from a COND_EXPR rather than from compare-and-branch gcc.target/i386/pr54855-9.c by producing extra moves while the corresponding min/max operations are now already synthesized by RTL expansion, register selection isn't optimal. This can be also provoked without this change by altering the operand order in the source. I have XFAILed that part of the test. Bootstrapped and tested on x86_64-unknown-linux-gnu ontop of the patch fixing if-converted RTL expansion when constants are involved. Comments welcome but I plan to push this once that dependency is acked. Thanks, Richard. PR tree-optimization/88540 * tree-ssa-phiopt.cc (minmax_replacement): Do not give up with NaNs but handle the simple case by if-converting to a COND_EXPR. * gcc.target/i386/pr88540.c: New testcase. * gcc.target/i386/pr54855-9.c: XFAIL check for redundant moves. * gcc.target/i386/pr54855-12.c: Adjust. * gcc.target/i386/pr54855-13.c: Likewise. * gcc.dg/tree-ssa/split-path-12.c: Likewise. --- gcc/testsuite/gcc.dg/tree-ssa/split-path-12.c | 4 +++- gcc/testsuite/gcc.target/i386/pr54855-12.c | 2 +- gcc/testsuite/gcc.target/i386/pr54855-13.c | 2 +- gcc/testsuite/gcc.target/i386/pr54855-9.c | 4 ++-- gcc/testsuite/gcc.target/i386/pr88540.c | 10 +++++++++ gcc/tree-ssa-phiopt.cc | 21 ++++++++++++++----- 6 files changed, 33 insertions(+), 10 deletions(-) create mode 100644 gcc/testsuite/gcc.target/i386/pr88540.c diff --git a/gcc/testsuite/gcc.dg/tree-ssa/split-path-12.c b/gcc/testsuite/gcc.dg/tree-ssa/split-path-12.c index 19a130d9bf1..da00f795ef0 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/split-path-12.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/split-path-12.c @@ -16,4 +16,6 @@ foo(double *d1, double *d2, double *d3, int num, double *ip) return dmax[0] + dmax[1] + dmax[2]; } -/* { dg-final { scan-tree-dump "appears to be optimized to a join point for if-convertable half-diamond" "split-paths" } } */ +/* Split-paths shouldn't do anything here, if there's a diamond it would + be if-convertible. */ +/* { dg-final { scan-tree-dump-not "Duplicating join block" "split-paths" } } */ diff --git a/gcc/testsuite/gcc.target/i386/pr54855-12.c b/gcc/testsuite/gcc.target/i386/pr54855-12.c index 2f8af392c83..09e8ab8ae39 100644 --- a/gcc/testsuite/gcc.target/i386/pr54855-12.c +++ b/gcc/testsuite/gcc.target/i386/pr54855-12.c @@ -1,6 +1,6 @@ /* { dg-do compile } */ /* { dg-options "-O2 -mavx512fp16" } */ -/* { dg-final { scan-assembler-times "vmaxsh\[ \\t\]" 1 } } */ +/* { dg-final { scan-assembler-times "vm\[ai\]\[nx\]sh\[ \\t\]" 1 } } */ /* { dg-final { scan-assembler-not "vcomish\[ \\t\]" } } */ /* { dg-final { scan-assembler-not "vmovsh\[ \\t\]" { target { ! ia32 } } } } */ diff --git a/gcc/testsuite/gcc.target/i386/pr54855-13.c b/gcc/testsuite/gcc.target/i386/pr54855-13.c index 87b4f459a5a..a4f25066f81 100644 --- a/gcc/testsuite/gcc.target/i386/pr54855-13.c +++ b/gcc/testsuite/gcc.target/i386/pr54855-13.c @@ -1,6 +1,6 @@ /* { dg-do compile } */ /* { dg-options "-O2 -mavx512fp16" } */ -/* { dg-final { scan-assembler-times "vmaxsh\[ \\t\]" 1 } } */ +/* { dg-final { scan-assembler-times "vm\[ai\]\[nx\]sh\[ \\t\]" 1 } } */ /* { dg-final { scan-assembler-not "vcomish\[ \\t\]" } } */ /* { dg-final { scan-assembler-not "vmovsh\[ \\t\]" { target { ! ia32 } } } } */ diff --git a/gcc/testsuite/gcc.target/i386/pr54855-9.c b/gcc/testsuite/gcc.target/i386/pr54855-9.c index 40add5f6763..fe9302e5077 100644 --- a/gcc/testsuite/gcc.target/i386/pr54855-9.c +++ b/gcc/testsuite/gcc.target/i386/pr54855-9.c @@ -1,8 +1,8 @@ /* { dg-do compile } */ /* { dg-options "-O2 -msse2 -mfpmath=sse" } */ /* { dg-final { scan-assembler-times "minss" 1 } } */ -/* { dg-final { scan-assembler-not "movaps" } } */ -/* { dg-final { scan-assembler-not "movss" } } */ +/* { dg-final { scan-assembler-not "movaps" { xfail *-*-* } } } */ +/* { dg-final { scan-assembler-not "movss" { xfail *-*-* } } } */ typedef float vec __attribute__((vector_size(16))); diff --git a/gcc/testsuite/gcc.target/i386/pr88540.c b/gcc/testsuite/gcc.target/i386/pr88540.c new file mode 100644 index 00000000000..b927d0c57d5 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr88540.c @@ -0,0 +1,10 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -msse2" } */ + +void test(double* __restrict d1, double* __restrict d2, double* __restrict d3) +{ + for (int n = 0; n < 2; ++n) + d3[n] = d1[n] < d2[n] ? d1[n] : d2[n]; +} + +/* { dg-final { scan-assembler "minpd" } } */ diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc index 467c9fd108a..13ee486831d 100644 --- a/gcc/tree-ssa-phiopt.cc +++ b/gcc/tree-ssa-phiopt.cc @@ -1580,10 +1580,6 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb, basic_block alt_ tree type = TREE_TYPE (PHI_RESULT (phi)); - /* The optimization may be unsafe due to NaNs. */ - if (HONOR_NANS (type) || HONOR_SIGNED_ZEROS (type)) - return false; - gcond *cond = as_a <gcond *> (*gsi_last_bb (cond_bb)); enum tree_code cmp = gimple_cond_code (cond); tree rhs = gimple_cond_rhs (cond); @@ -1770,6 +1766,9 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb, basic_block alt_ else return false; } + else if (HONOR_NANS (type) || HONOR_SIGNED_ZEROS (type)) + /* The optimization may be unsafe due to NaNs. */ + return false; else if (middle_bb != alt_middle_bb && threeway_p) { /* Recognize the following case: @@ -2103,7 +2102,19 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb, basic_block alt_ /* Emit the statement to compute min/max. */ gimple_seq stmts = NULL; tree phi_result = PHI_RESULT (phi); - result = gimple_build (&stmts, minmax, TREE_TYPE (phi_result), arg0, arg1); + + /* When we can't use a MIN/MAX_EXPR still make sure the expression + stays in a form to be recognized by ISA that map to IEEE x > y ? x : y + semantics (that's not IEEE max semantics). */ + if (HONOR_NANS (type) || HONOR_SIGNED_ZEROS (type)) + { + result = gimple_build (&stmts, cmp, boolean_type_node, + gimple_cond_lhs (cond), rhs); + result = gimple_build (&stmts, COND_EXPR, TREE_TYPE (phi_result), + result, arg_true, arg_false); + } + else + result = gimple_build (&stmts, minmax, TREE_TYPE (phi_result), arg0, arg1); gsi = gsi_last_bb (cond_bb); gsi_insert_seq_before (&gsi, stmts, GSI_NEW_STMT); -- 2.35.3