[PATCH v2] aarch64: simplify RCPC3 unpredictable logic
Jan Beulich
jbeulich@suse.com
Fri Mar 7 09:07:31 GMT 2025
The original observation was that STILP is warned about when everything
is fine. Documentation, not just for STILP, says explicitly that
behavior is identical to respective pre-existing insns (for STILP in
particular that's STP). With that it's unclear why distinct logic was
added: Other code can be re-used, simply distinguishing by the number of
operands. This was diagnostics also end up more consistent.
Along with adding some STILP uses to the (positive) testcase, also add a
pair of STLR to similarly demonstrate that the register overlap goes
without warning when there's no write-back.
---
See https://sourceware.org/pipermail/binutils/2024-August/136404.html.
Note also how "load pair transfer" was quite odd in the diagnostic for
STILP being a store, not a load.
---
v2: Testcase adjustments as per review feedback.
--- a/gas/config/tc-aarch64.c
+++ b/gas/config/tc-aarch64.c
@@ -8465,6 +8465,7 @@ warn_unpredictable_ldst (aarch64_instruc
case ldst_imm10:
case ldst_unscaled:
case ldst_unpriv:
+ ldst_single:
/* Loading/storing the base register is unpredictable if writeback. */
if ((aarch64_get_operand_class (opnds[0].type)
== AARCH64_OPND_CLASS_INT_REG)
@@ -8477,43 +8478,9 @@ warn_unpredictable_ldst (aarch64_instruc
break;
case rcpc3:
- {
- const int nb_operands = aarch64_num_of_operands (opcode);
- if (aarch64_get_operand_class (opnds[0].type)
- == AARCH64_OPND_CLASS_INT_REG)
- {
- /* Load Pair transfer with register overlap. */
- if (nb_operands == 3 && opnds[0].reg.regno == opnds[1].reg.regno)
- { // ldiapp, stilp
- as_warn (_("unpredictable load pair transfer with register "
- "overlap -- `%s'"),
- str);
- }
- /* Loading/storing the base register is unpredictable if writeback. */
- else if ((nb_operands == 2
- && opnds[0].reg.regno == opnds[1].addr.base_regno
- && opnds[1].addr.base_regno != REG_SP
- && opnds[1].addr.writeback)
- || (nb_operands == 3
- && (opnds[0].reg.regno == opnds[2].addr.base_regno
- || opnds[1].reg.regno == opnds[2].addr.base_regno)
- && opnds[2].addr.base_regno != REG_SP
- && opnds[2].addr.writeback))
- {
- if (strcmp (opcode->name, "ldapr") == 0
- || strcmp (opcode->name, "ldiapp") == 0)
- as_warn (
- _("unpredictable transfer with writeback (load) -- `%s'"),
- str);
- else // stlr, stilp
- as_warn (
- _("unpredictable transfer with writeback (store) -- `%s'"),
- str);
- }
- }
- }
- break;
-
+ if (aarch64_num_of_operands (opcode) == 2)
+ goto ldst_single;
+ /* Fall through. */
case ldstpair_off:
case ldstnapair_offs:
case ldstpair_indexed:
--- a/gas/testsuite/gas/aarch64/rcpc3.d
+++ b/gas/testsuite/gas/aarch64/rcpc3.d
@@ -28,8 +28,10 @@ Disassembly of section \.text:
[^:]+: 99010860 stilp w0, w1, \[x3, #-8\]!
[^:]+: d9011820 stilp x0, x1, \[x1\]
[^:]+: d9011800 stilp x0, x1, \[x0\]
+[^:]+: d9001800 stilp x0, x0, \[x0\]
[^:]+: 99011820 stilp w0, w1, \[x1\]
[^:]+: 99011800 stilp w0, w1, \[x0\]
+[^:]+: 99001800 stilp w0, w0, \[x0\]
[^:]+: b8bfc020 ldapr w0, \[x1\]
[^:]+: b8bfc020 ldapr w0, \[x1\]
[^:]+: f8bfc020 ldapr x0, \[x1\]
@@ -44,8 +46,10 @@ Disassembly of section \.text:
[^:]+: d9c00be0 ldapr x0, \[sp\], #8
[^:]+: 889ffc20 stlr w0, \[x1\]
[^:]+: 889ffc20 stlr w0, \[x1\]
+[^:]+: 889ffc00 stlr w0, \[x0\]
[^:]+: c89ffc20 stlr x0, \[x1\]
[^:]+: c89ffc20 stlr x0, \[x1\]
+[^:]+: c89ffc00 stlr x0, \[x0\]
[^:]+: 99800841 stlr w1, \[x2, #-4\]!
[^:]+: d9800841 stlr x1, \[x2, #-8\]!
[^:]+: d980081e stlr x30, \[x0, #-8\]!
--- a/gas/testsuite/gas/aarch64/rcpc3.s
+++ b/gas/testsuite/gas/aarch64/rcpc3.s
@@ -29,8 +29,10 @@
// for store is fine.
stilp x0, x1, [x1]
stilp x0, x1, [x0]
+ stilp x0, x0, [x0]
stilp w0, w1, [x1]
stilp w0, w1, [x0]
+ stilp w0, w0, [x0]
ldapr w0, [x1]
ldapr w0, [x1, #0]
@@ -47,8 +49,10 @@
stlr w0, [x1]
stlr w0, [x1, #0]
+ stlr w0, [x0]
stlr x0, [x1]
stlr x0, [x1, #0]
+ stlr x0, [x0]
stlr w1, [x2, #-4]!
stlr x1, [x2, #-8]!
stlr x30, [x0, #-8]!
--- a/gas/testsuite/gas/aarch64/rcpc3-fail.l
+++ b/gas/testsuite/gas/aarch64/rcpc3-fail.l
@@ -51,27 +51,23 @@
.*: Error: invalid increment amount at operand 2 -- `stlr x0,\[x1,#-4\]!'
.*: Error: invalid increment amount at operand 2 -- `stlr w0,\[x1,#4\]!'
.*: Error: invalid increment amount at operand 2 -- `stlr x0,\[x1,#8\]!'
-.*: Warning: unpredictable load pair transfer with register overlap -- `ldiapp w0,w0,\[x1\]'
-.*: Warning: unpredictable load pair transfer with register overlap -- `ldiapp x0,x0,\[x1\]'
-.*: Warning: unpredictable load pair transfer with register overlap -- `ldiapp w0,w0,\[x1\],#8'
-.*: Warning: unpredictable load pair transfer with register overlap -- `ldiapp x0,x0,\[x1\],#16'
-.*: Warning: unpredictable load pair transfer with register overlap -- `stilp w0,w0,\[x1\]'
-.*: Warning: unpredictable load pair transfer with register overlap -- `stilp x0,x0,\[x1\]'
-.*: Warning: unpredictable load pair transfer with register overlap -- `stilp w0,w0,\[x1,#-8\]!'
-.*: Warning: unpredictable load pair transfer with register overlap -- `stilp x0,x0,\[x1,#-16\]!'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldiapp x0,x1,\[x0\],#16'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldiapp x0,x1,\[x1\],#16'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldiapp w0,w1,\[x0\],#8'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldiapp w0,w1,\[x1\],#8'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldapr x0,\[x0\],#8'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldapr w0,\[x0\],#4'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldapr x1,\[x1\],#8'
-.*: Warning: unpredictable transfer with writeback \(load\) -- `ldapr x30,\[x30\],#8'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stilp x0,x1,\[x1,#-16\]!'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stilp w0,w1,\[x1,#-8\]!'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stilp x0,x1,\[x0,#-16\]!'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stilp w0,w1,\[x0,#-8\]!'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stlr x0,\[x0,#-8\]!'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stlr w0,\[x0,#-4\]!'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stlr x1,\[x1,#-8\]!'
-.*: Warning: unpredictable transfer with writeback \(store\) -- `stlr x30,\[x30,#-8\]!'
\ No newline at end of file
+.*: Warning: unpredictable load of register pair -- `ldiapp w0,w0,\[x1\]'
+.*: Warning: unpredictable load of register pair -- `ldiapp x0,x0,\[x1\]'
+.*: Warning: unpredictable load of register pair -- `ldiapp w0,w0,\[x1\],#8'
+.*: Warning: unpredictable load of register pair -- `ldiapp x0,x0,\[x1\],#16'
+.*: Warning: unpredictable transfer with writeback -- `ldiapp x0,x1,\[x0\],#16'
+.*: Warning: unpredictable transfer with writeback -- `ldiapp x0,x1,\[x1\],#16'
+.*: Warning: unpredictable transfer with writeback -- `ldiapp w0,w1,\[x0\],#8'
+.*: Warning: unpredictable transfer with writeback -- `ldiapp w0,w1,\[x1\],#8'
+.*: Warning: unpredictable transfer with writeback -- `ldapr x0,\[x0\],#8'
+.*: Warning: unpredictable transfer with writeback -- `ldapr w0,\[x0\],#4'
+.*: Warning: unpredictable transfer with writeback -- `ldapr x1,\[x1\],#8'
+.*: Warning: unpredictable transfer with writeback -- `ldapr x30,\[x30\],#8'
+.*: Warning: unpredictable transfer with writeback -- `stilp x0,x1,\[x1,#-16\]!'
+.*: Warning: unpredictable transfer with writeback -- `stilp w0,w1,\[x1,#-8\]!'
+.*: Warning: unpredictable transfer with writeback -- `stilp x0,x1,\[x0,#-16\]!'
+.*: Warning: unpredictable transfer with writeback -- `stilp w0,w1,\[x0,#-8\]!'
+.*: Warning: unpredictable transfer with writeback -- `stlr x0,\[x0,#-8\]!'
+.*: Warning: unpredictable transfer with writeback -- `stlr w0,\[x0,#-4\]!'
+.*: Warning: unpredictable transfer with writeback -- `stlr x1,\[x1,#-8\]!'
+.*: Warning: unpredictable transfer with writeback -- `stlr x30,\[x30,#-8\]!'
--- a/gas/testsuite/gas/aarch64/rcpc3-fail.s
+++ b/gas/testsuite/gas/aarch64/rcpc3-fail.s
@@ -81,11 +81,6 @@
ldiapp w0, w0, [x1], #8
ldiapp x0, x0, [x1], #16
- stilp w0, w0, [x1]
- stilp x0, x0, [x1]
- stilp w0, w0, [x1, #-8]!
- stilp x0, x0, [x1, #-16]!
-
/* Invalid write back overlap (load)*/
ldiapp x0, x1, [x0], #16
ldiapp x0, x1, [x1], #16
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