https://gcc.gnu.org/g:4853bebb4dd07ffa6d836f3a8f630188e3180662
commit 4853bebb4dd07ffa6d836f3a8f630188e3180662
Author: Jeff Law <j...@ventanamicro.com>
Date: Sun May 12 07:05:43 2024 -0600
[to-be-committed] RISC-V Fix minor regression in synthesis WRT bseti usage
Overnight testing showed a small number of cases where constant synthesis
was
doing something dumb. Specifically generating more instructions than the
number of bits set in the constant.
It was a minor goof in the recent bseti code. In the code to first figure
out
what bits LUI could set, I included one bit outside the space LUI operates.
For some dumb reason I kept thinking in terms of 11 low bits belonging to
addi,
but it's actually 12 bits. The net is what we thought should be a single
LUI
for costing turned into LUI+ADDI.
I didn't let the test run to completion, but over the course of 12 hours it
found 9 cases. Given we know that the triggers all have 0x800 set, I bet we
could likely find more, but I doubt it's that critical to cover every
possible
constant that regressed.
gcc/
* config/riscv/riscv.cc (riscv_build_integer_1): Fix thinko in
testing
when lui can be used to set several bits in bseti path.
gcc/testsuite
* gcc.target/riscv/synthesis-4.c: New test
(cherry picked from commit 77a28ed91b2a527b9006ee1a220b468756b43eca)
Diff:
---
gcc/config/riscv/riscv.cc | 6 ++---
gcc/testsuite/gcc.target/riscv/synthesis-4.c | 34 ++++++++++++++++++++++++++++
2 files changed, 37 insertions(+), 3 deletions(-)
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 9c98b1da035..049f8f8cb9f 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -921,12 +921,12 @@ riscv_build_integer_1 (struct riscv_integer_op
codes[RISCV_MAX_INTEGER_OPS],
/* First handle any bits set by LUI. Be careful of the
SImode sign bit!. */
- if (value & 0x7ffff800)
+ if (value & 0x7ffff000)
{
alt_codes[i].code = (i == 0 ? UNKNOWN : IOR);
- alt_codes[i].value = value & 0x7ffff800;
+ alt_codes[i].value = value & 0x7ffff000;
alt_codes[i].use_uw = false;
- value &= ~0x7ffff800;
+ value &= ~0x7ffff000;
i++;
}
diff --git a/gcc/testsuite/gcc.target/riscv/synthesis-4.c
b/gcc/testsuite/gcc.target/riscv/synthesis-4.c
new file mode 100644
index 00000000000..328a55b9e6e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/synthesis-4.c
@@ -0,0 +1,34 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target rv64 } */
+/* We aggressively skip as we really just need to test the basic synthesis
+ which shouldn't vary based on the optimization level. -O1 seems to work
+ and eliminates the usual sources of extraneous dead code that would throw
+ off the counts. */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" "-O2" "-O3" "-Os" "-Oz" "-flto" } }
*/
+/* { dg-options "-march=rv64gc_zba_zbb_zbs" } */
+
+/* Rather than test for a specific synthesis of all these constants or
+ having thousands of tests each testing one variant, we just test the
+ total number of instructions.
+
+ This isn't expected to change much and any change is worthy of a look. */
+/* { dg-final { scan-assembler-times
"\\t(add|addi|bseti|li|ret|sh1add|sh2add|sh3add|slli)" 45 } } */
+
+
+unsigned long foo_0x60000400000800(void) { return 0x60000400000800UL; }
+
+unsigned long foo_0xc0000400000800(void) { return 0xc0000400000800UL; }
+
+unsigned long foo_0x180000400000800(void) { return 0x180000400000800UL; }
+
+unsigned long foo_0x300000400000800(void) { return 0x300000400000800UL; }
+
+unsigned long foo_0x600000400000800(void) { return 0x600000400000800UL; }
+
+unsigned long foo_0xc00000400000800(void) { return 0xc00000400000800UL; }
+
+unsigned long foo_0x1800000400000800(void) { return 0x1800000400000800UL; }
+
+unsigned long foo_0x3000000400000800(void) { return 0x3000000400000800UL; }
+
+unsigned long foo_0x6000000400000800(void) { return 0x6000000400000800UL; }
