On Thu, 2019-02-07 at 18:13 +0000, Wilco Dijkstra wrote:
> External Email
>
> Hi Steve,
>
> > > After special cases you could do something like t = mask2 +
> > > (HWI_1U << shift);
> > > return t == (t & -t) to check for a valid bfi.
> >
> > I am not sure I follow this logic and my attempts to use this did not
> > work so I kept my original code.
>
> It's similar to the initial code in aarch64_bitmask_imm, but rather than
> adding
> the lowest bit to the value to verify it is a mask (val + (val & -val)), we
> use the
> shift instead. If the shift is exactly right, it reaches the first
> set bit of the mask.
> Adding the low bit to a valid mask always results in zero or a single set bit.
> The standard idiom to check that is t == (t & -t).
>
> > > + "bfi\t%<GPI:w>0, %<GPI:w>1, 0, %P2"
> > >
> > > This could emit a width that may be 32 too large in SImode if bit 31 is
> > > set
> > > (there is another use of %P in aarch64.md which may have the same
> > > issue).
> >
> > I am not sure why having bit 31 set would be a problem. Sign
> > extension?
>
> Yes, if bit 31 is set, %P will emit 33 for a 32-bit constant which is
> obviously wrong.
> Your patch avoids this for bfi by explicitly computing the correct value.
>
> This looks good to me (and creates useful bfi's as expected), but I
> can't approve.
>
> Wilco
Thanks for looking this over. I have updated the mask check to use
your method and retested to make sure it still works. Can one of the
aarch64 maintainers approve this patch?
2018-02-11 Steve Ellcey <[email protected]>
PR rtl-optimization/87763
* config/aarch64/aarch64-protos.h (aarch64_masks_and_shift_for_bfi_p):
New prototype.
* config/aarch64/aarch64.c (aarch64_masks_and_shift_for_bfi_p):
New function.
* config/aarch64/aarch64.md (*aarch64_bfi<GPI:mode>5_shift):
New instruction.
(*aarch64_bfi<GPI:mode>4_noand): Ditto.
(*aarch64_bfi<GPI:mode>4_noshift): Ditto.
(*aarch64_bfi<GPI:mode>4_noshift_alt): Ditto.
2018-02-11 Steve Ellcey <[email protected]>
PR rtl-optimization/87763
* gcc.target/aarch64/combine_bfxil.c: Change some bfxil checks
to bfi.
* gcc.target/aarch64/combine_bfi_2.c: New test.
diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index b035e35f33b..b6c0d0a8eb6 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -429,6 +429,9 @@ bool aarch64_label_mentioned_p (rtx);
void aarch64_declare_function_name (FILE *, const char*, tree);
bool aarch64_legitimate_pic_operand_p (rtx);
bool aarch64_mask_and_shift_for_ubfiz_p (scalar_int_mode, rtx, rtx);
+bool aarch64_masks_and_shift_for_bfi_p (scalar_int_mode, unsigned HOST_WIDE_INT,
+ unsigned HOST_WIDE_INT,
+ unsigned HOST_WIDE_INT);
bool aarch64_zero_extend_const_eq (machine_mode, rtx, machine_mode, rtx);
bool aarch64_move_imm (HOST_WIDE_INT, machine_mode);
opt_machine_mode aarch64_sve_pred_mode (unsigned int);
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index d7c453cdad0..a7ef952ad1b 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -9330,6 +9330,35 @@ aarch64_mask_and_shift_for_ubfiz_p (scalar_int_mode mode, rtx mask,
& ((HOST_WIDE_INT_1U << INTVAL (shft_amnt)) - 1)) == 0;
}
+/* Return true if the masks and a shift amount from an RTX of the form
+ ((x & MASK1) | ((y << SHIFT_AMNT) & MASK2)) are valid to combine into
+ a BFI instruction of mode MODE. See *arch64_bfi patterns. */
+
+bool
+aarch64_masks_and_shift_for_bfi_p (scalar_int_mode mode,
+ unsigned HOST_WIDE_INT mask1,
+ unsigned HOST_WIDE_INT shft_amnt,
+ unsigned HOST_WIDE_INT mask2)
+{
+ unsigned HOST_WIDE_INT t;
+
+ /* Verify that there is no overlap in what bits are set in the two masks. */
+ if (mask1 != ~mask2)
+ return false;
+
+ /* Verify that mask2 is not all zeros or ones. */
+ if (mask2 == 0 || mask2 == HOST_WIDE_INT_M1U)
+ return false;
+
+ /* The shift amount should always be less than the mode size. */
+ gcc_assert (shft_amnt < GET_MODE_BITSIZE (mode));
+
+ /* Verify that the mask being shifted is contiguous and would be in the
+ least significant bits after shifting by shft_amnt. */
+ t = mask2 + (HOST_WIDE_INT_1U << shft_amnt);
+ return (t == (t & -t));
+}
+
/* Calculate the cost of calculating X, storing it in *COST. Result
is true if the total cost of the operation has now been calculated. */
static bool
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index b7f6fe0f135..2bbd3f1055c 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -5476,6 +5476,76 @@
[(set_attr "type" "bfm")]
)
+;; Match a bfi instruction where the shift of OP3 means that we are
+;; actually copying the least significant bits of OP3 into OP0 by way
+;; of the AND masks and the IOR instruction. A similar instruction
+;; with the two parts of the IOR swapped around was never triggered
+;; in a bootstrap build and test of GCC so it was not included.
+
+(define_insn "*aarch64_bfi<GPI:mode>5_shift"
+ [(set (match_operand:GPI 0 "register_operand" "=r")
+ (ior:GPI (and:GPI (match_operand:GPI 1 "register_operand" "0")
+ (match_operand:GPI 2 "const_int_operand" "n"))
+ (and:GPI (ashift:GPI
+ (match_operand:GPI 3 "register_operand" "r")
+ (match_operand:GPI 4 "aarch64_simd_shift_imm_<mode>" "n"))
+ (match_operand:GPI 5 "const_int_operand" "n"))))]
+ "aarch64_masks_and_shift_for_bfi_p (<MODE>mode, UINTVAL (operands[2]),
+ UINTVAL (operands[4]),
+ UINTVAL(operands[5]))"
+ "bfi\t%<GPI:w>0, %<GPI:w>3, %4, %P5"
+ [(set_attr "type" "bfm")]
+)
+
+;; Like *aarch64_bfi<GPI:mode>5_shift but with no and of the ashift because
+;; the shift is large enough to remove the need for an AND instruction.
+
+(define_insn "*aarch64_bfi<GPI:mode>4_noand"
+ [(set (match_operand:GPI 0 "register_operand" "=r")
+ (ior:GPI (and:GPI (match_operand:GPI 1 "register_operand" "0")
+ (match_operand:GPI 2 "const_int_operand" "n"))
+ (ashift:GPI
+ (match_operand:GPI 3 "register_operand" "r")
+ (match_operand:GPI 4 "aarch64_simd_shift_imm_<mode>" "n"))))]
+ "aarch64_masks_and_shift_for_bfi_p (<MODE>mode, UINTVAL (operands[2]),
+ UINTVAL (operands[4]),
+ HOST_WIDE_INT_M1U << UINTVAL (operands[4]) )"
+{
+ operands[5] = GEN_INT (GET_MODE_BITSIZE (<MODE>mode) - UINTVAL (operands[4]));
+ return "bfi\t%<GPI:w>0, %<GPI:w>3, %4, %5";
+}
+ [(set_attr "type" "bfm")]
+)
+
+;; Like *aarch64_bfi<GPI:mode>5_shift but with no shifting, we are just
+;; copying the least significant bits of OP3 to OP0. In this case we do
+;; need two versions of the instruction to handle different checks on the
+;; constant values.
+
+(define_insn "*aarch64_bfi<GPI:mode>4_noshift"
+ [(set (match_operand:GPI 0 "register_operand" "=r")
+ (ior:GPI (and:GPI (match_operand:GPI 1 "register_operand" "0")
+ (match_operand:GPI 2 "const_int_operand" "n"))
+ (and:GPI (match_operand:GPI 3 "register_operand" "r")
+ (match_operand:GPI 4 "const_int_operand" "n"))))]
+ "aarch64_masks_and_shift_for_bfi_p (<MODE>mode, UINTVAL (operands[2]), 0,
+ UINTVAL (operands[4]))"
+ "bfi\t%<GPI:w>0, %<GPI:w>3, 0, %P4"
+ [(set_attr "type" "bfm")]
+)
+
+(define_insn "*aarch64_bfi<GPI:mode>4_noshift_alt"
+ [(set (match_operand:GPI 0 "register_operand" "=r")
+ (ior:GPI (and:GPI (match_operand:GPI 1 "register_operand" "r")
+ (match_operand:GPI 2 "const_int_operand" "n"))
+ (and:GPI (match_operand:GPI 3 "register_operand" "0")
+ (match_operand:GPI 4 "const_int_operand" "n"))))]
+ "aarch64_masks_and_shift_for_bfi_p (<MODE>mode, UINTVAL (operands[4]), 0,
+ UINTVAL (operands[2]))"
+ "bfi\t%<GPI:w>0, %<GPI:w>1, 0, %P2"
+ [(set_attr "type" "bfm")]
+)
+
(define_insn "*extr_insv_lower_reg<mode>"
[(set (zero_extract:GPI (match_operand:GPI 0 "register_operand" "+r")
(match_operand 1 "const_int_operand" "n")
diff --git a/gcc/testsuite/gcc.target/aarch64/combine_bfi_2.c b/gcc/testsuite/gcc.target/aarch64/combine_bfi_2.c
index e69de29bb2d..145282d4d55 100644
--- a/gcc/testsuite/gcc.target/aarch64/combine_bfi_2.c
+++ b/gcc/testsuite/gcc.target/aarch64/combine_bfi_2.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int f1(int x, int y)
+{
+ return (y & 0xfffffff) | (((x <<28) & 0xf0000000));
+}
+
+
+int f2(int x, int y)
+{
+ return (((x <<28) & 0xf0000000)) | (y & 0xfffffff);
+}
+
+/* { dg-final { scan-assembler-times {\tbfi\t} 2 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/combine_bfxil.c b/gcc/testsuite/gcc.target/aarch64/combine_bfxil.c
index 109f989a2f0..c3b5fc58800 100644
--- a/gcc/testsuite/gcc.target/aarch64/combine_bfxil.c
+++ b/gcc/testsuite/gcc.target/aarch64/combine_bfxil.c
@@ -114,4 +114,5 @@ main (void)
return 0;
}
-/* { dg-final { scan-assembler-times "bfxil\\t" 18 } } */
+/* { dg-final { scan-assembler-times "bfxil\\t" 3 } } */
+/* { dg-final { scan-assembler-times "bfi\\t" 15 } } */
