[RISC-V][PR target/119971] Avoid losing shift count masking

As is outlined in the PR, we have a few define_insn_and_split patterns which
optimize away explicit masking of shift/bit positions when the masking matches
what the hardware's behavior.

A small number of those define_insn_and_split patterns generate a single
instruction.  It's fairly elegant in that we were essentially just rewriting
the RTL to match an existing pattern.

In one case we'd do the rewriting and later turn a 32bit shift into a bset.
That's not safe because the masking of a 32bit shift uses 0x1f while masking on
bset uses 0x3f on rv64.   The net was incorrect code as seen in the BZ entry.

The fix is pretty simple.  There's no real reason we need to use a
define_insn_and_split.  It was just convenient.  Instead we can use a simple
define_insn.  That avoids a change in the masking behavior for the shift
count/bit position and the masking stays in the RTL.

I quickly scanned the entire port and didn't see any additional
define_insn_and_splits that obviously generated a single instruction outside
the shift/rotate space, though in the vector space that's nontrivial to
ascertain.

This was been run through my tester for the cross configurations, but not the
native bootstrap/regression test (yet).

	PR target/119971
gcc/
	* config/riscv/bitmanip.md (rotation with masked count): Rewrite
	as define_insn patterns.  Fix formatting.
	* config/riscv/riscv.md (shift with masked count): Similarly.

gcc/testsuite
	* gcc.target/riscv/pr119971.c: New test.
	* gcc.target/riscv/zbb-rol-ror-03.c: Adjust test slightly.

(cherry picked from commit 05d75c5bfcf923bc0258b79a08c5861590c5a2b9)

diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index 5ed5e18cb36a898000ef888eb3a7303ae75f7a0b..320531cd1ed00463002f04c7c043fe158442c960 100644 (file)
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -423,39 +423,40 @@
   "rolw\t%0,%1,%2"
   [(set_attr "type" "bitmanip")])
 
-(define_insn_and_split "*<bitmanip_optab><GPR:mode>3_mask"
-  [(set (match_operand:GPR     0 "register_operand" "= r")
-        (bitmanip_rotate:GPR
-            (match_operand:GPR 1 "register_operand" "  r")
-            (match_operator 4 "subreg_lowpart_operator"
-             [(and:GPR2
-               (match_operand:GPR2 2 "register_operand"  "r")
-               (match_operand 3 "<GPR:shiftm1>" "<GPR:shiftm1p>"))])))]
+(define_insn "*<bitmanip_optab><mode>3_mask"
+  [(set (match_operand:X 0 "register_operand" "=r")
+       (bitmanip_rotate:X
+         (match_operand:X 1 "register_operand" "r")
+         (match_operator 4 "subreg_lowpart_operator"
+           [(and:X (match_operand:X 2 "register_operand"  "r")
+                   (match_operand 3 "<X:shiftm1>" "<X:shiftm1p>"))])))]
   "TARGET_ZBB || TARGET_ZBKB"
-  "#"
-  "&& 1"
-  [(set (match_dup 0)
-        (bitmanip_rotate:GPR (match_dup 1)
-                             (match_dup 2)))]
-  "operands[2] = gen_lowpart (QImode, operands[2]);"
+  "<bitmanip_insn>\t%0,%1,%2"
   [(set_attr "type" "bitmanip")
-   (set_attr "mode" "<GPR:MODE>")])
+   (set_attr "mode" "<X:MODE>")])
 
-(define_insn_and_split "*<bitmanip_optab>si3_sext_mask"
-  [(set (match_operand:DI     0 "register_operand" "= r")
-  (sign_extend:DI (bitmanip_rotate:SI
-            (match_operand:SI 1 "register_operand" "  r")
-            (match_operator 4 "subreg_lowpart_operator"
-             [(and:GPR
-               (match_operand:GPR 2 "register_operand"  "r")
-               (match_operand 3 "const_si_mask_operand"))]))))]
+(define_insn "*<bitmanip_optab>3_mask_si"
+  [(set (match_operand:SI 0 "register_operand" "=r")
+       (bitmanip_rotate:SI
+         (match_operand:SI 1 "register_operand" "r")
+         (match_operator 3 "subreg_lowpart_operator"
+           [(and:X (match_operand:SI 2 "register_operand"  "r")
+                   (const_int 31))])))]
   "TARGET_64BIT && (TARGET_ZBB || TARGET_ZBKB)"
-  "#"
-  "&& 1"
-  [(set (match_dup 0)
-  (sign_extend:DI (bitmanip_rotate:SI (match_dup 1)
-                           (match_dup 2))))]
-  "operands[2] = gen_lowpart (QImode, operands[2]);"
+  "<bitmanip_insn>w\t%0,%1,%2"
+  [(set_attr "type" "bitmanip")
+   (set_attr "mode" "SI")])
+
+(define_insn "*<bitmanip_optab>si3_sext_mask"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+       (sign_extend:DI
+         (bitmanip_rotate:SI
+           (match_operand:SI 1 "register_operand" "r")
+           (match_operator 3 "subreg_lowpart_operator"
+             [(and:X (match_operand:GPR 2 "register_operand"  "r")
+                     (const_int 31))]))))]
+  "TARGET_64BIT && (TARGET_ZBB || TARGET_ZBKB)"
+  "<bitmanip_insn>w\t%0,%1,%2"
   [(set_attr "type" "bitmanip")
    (set_attr "mode" "DI")])
 

diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 26a247c2b9660ade84c479715b2ec80132eba2ec..c551a1fa4e2794f503ef3222a193259755944a1c 100644 (file)
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -2922,7 +2922,7 @@
   [(set_attr "type" "shift")
    (set_attr "mode" "DI")])
 
-(define_insn_and_split "*<optab><GPR:mode>3_mask_1"
+(define_insn "*<optab><GPR:mode>3_mask_1"
   [(set (match_operand:GPR     0 "register_operand" "= r")
        (any_shift:GPR
            (match_operand:GPR 1 "register_operand" "  r")
@@ -2931,12 +2931,7 @@
               (match_operand:GPR2 2 "register_operand"  "r")
               (match_operand 3 "<GPR:shiftm1>"))])))]
   ""
-  "#"
-  "&& 1"
-  [(set (match_dup 0)
-       (any_shift:GPR (match_dup 1)
-                     (match_dup 2)))]
-  "operands[2] = gen_lowpart (QImode, operands[2]);"
+  "<insn>\t%0,%1,%2"
   [(set_attr "type" "shift")
    (set_attr "mode" "<GPR:MODE>")])
 
@@ -2955,7 +2950,7 @@
   [(set_attr "type" "shift")
    (set_attr "mode" "SI")])
 
-(define_insn_and_split "*<optab>si3_extend_mask"
+(define_insn "*<optab>si3_extend_mask"
   [(set (match_operand:DI                   0 "register_operand" "= r")
        (sign_extend:DI
            (any_shift:SI
@@ -2965,13 +2960,7 @@
                (match_operand:GPR 2 "register_operand" " r")
                (match_operand 3 "const_si_mask_operand"))]))))]
   "TARGET_64BIT"
-  "#"
-  "&& 1"
-  [(set (match_dup 0)
-       (sign_extend:DI
-        (any_shift:SI (match_dup 1)
-                      (match_dup 2))))]
-  "operands[2] = gen_lowpart (QImode, operands[2]);"
+  "<insn>w\t%0,%1,%2"
   [(set_attr "type" "shift")
    (set_attr "mode" "SI")])
 

diff --git a/gcc/testsuite/gcc.target/riscv/pr119971.c b/gcc/testsuite/gcc.target/riscv/pr119971.c
new file mode 100644 (file)
index 0000000..c3f23b0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr119971.c
@@ -0,0 +1,24 @@
+/* { dg-do compile { target rv64 } } */
+/* { dg-options "-march=rv64gcb -mabi=lp64" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-g" "-Oz" "-Os" } } */
+
+__attribute__ ((noipa)) unsigned
+foo (unsigned b, unsigned e, unsigned i)
+{
+  e >>= b;
+  i >>= e & 31;
+  return i & 1;
+}
+
+int main()
+{
+  if (foo (0x18, 0xfe000000, 0x40000000) != 1)
+    __builtin_abort ();
+  return 0;
+}
+
+/* { dg-final { scan-assembler-times "andi\t" 1 } } */
+/* { dg-final { scan-assembler-times "srlw\t" 2 } } */
+/* { dg-final { scan-assembler-not "bext\t" } } */
+
+

diff --git a/gcc/testsuite/gcc.target/riscv/zbb-rol-ror-03.c b/gcc/testsuite/gcc.target/riscv/zbb-rol-ror-03.c
index f85c20eb74ad37df385a84ae27b1bf9a4c9662d1..3121cb6bff48bb893babb64a1f1e3f368a14e938 100644 (file)
--- a/gcc/testsuite/gcc.target/riscv/zbb-rol-ror-03.c
+++ b/gcc/testsuite/gcc.target/riscv/zbb-rol-ror-03.c
@@ -10,7 +10,7 @@ unsigned int rol(unsigned int rs1, unsigned int rs2)
 }
 unsigned int ror(unsigned int rs1, unsigned int rs2)
 {
-    int shamt = rs2 & (64 - 1);
+    int shamt = rs2 & (32 - 1);
     return (rs1 >> shamt) | (rs1 << ((32 - shamt) & (32 - 1)));
 }