aarch64: Prevent streaming-compatible code from assembler rejection [PR121028]

Streaming-compatible functions can be compiled without SME enabled, but need
to use "SMSTART SM" and "SMSTOP SM" to temporarily switch into the streaming
state of a callee.  These switches are conditional on the current mode being
opposite to the target mode, so no SME instructions are executed if SME is not
available.

However, in GAS, "SMSTART SM" and "SMSTOP SM" always require +sme.  A call
from a streaming-compatible function, compiled without SME enabled, to a non
-streaming function will be rejected as:

Error: selected processor does not support `smstop sm'..

To work around this, we make use of the .inst directive to insert the literal
encodings of "SMSTART SM" and "SMSTOP SM".

gcc/ChangeLog:
	PR target/121028
	* config/aarch64/aarch64-sme.md (aarch64_smstart_sm): Use the .inst
	directive if !TARGET_SME.
	(aarch64_smstop_sm): Likewise.

gcc/testsuite/ChangeLog:
	PR target/121028
	* gcc.target/aarch64/sme/call_sm_switch_1.c: Tell check-function
	-bodies not to ignore .inst directives, and replace the test for
	"smstart sm" with one for it's encoding.
	* gcc.target/aarch64/sme/call_sm_switch_11.c: Likewise.
	* gcc.target/aarch64/sme/pr121028.c: New test.

(cherry picked from commit d52e9ef98bb30872482a46e7a2ec6a20c3ca4a4c)

diff --git a/gcc/config/aarch64/aarch64-sme.md b/gcc/config/aarch64/aarch64-sme.md
index f7958c90eae44d5f0b0decbab92dcc44010bbfc4..3673941ab8695110a7de3ddb1d2953ecc8d4c7d3 100644 (file)
--- a/gcc/config/aarch64/aarch64-sme.md
+++ b/gcc/config/aarch64/aarch64-sme.md
@@ -61,6 +61,10 @@
 ;; (b) they are sometimes used conditionally, particularly in streaming-
 ;; compatible code.
 ;;
+;; To prevent the latter from upsetting the assembler, we emit the literal
+;; encodings of "SMSTART SM" and "SMSTOP SM" when compiling without
+;; TARGET_SME.
+;;
 ;; =========================================================================
 
 ;; -------------------------------------------------------------------------
@@ -160,7 +164,9 @@
    (clobber (reg:VNx16BI P14_REGNUM))
    (clobber (reg:VNx16BI P15_REGNUM))]
   ""
-  "smstart\tsm"
+  {
+    return TARGET_SME ? "smstart\tsm" : ".inst 0xd503437f // smstart sm";
+  }
 )
 
 ;; Turn off streaming mode.  This clobbers all SVE state.
@@ -195,7 +201,9 @@
    (clobber (reg:VNx16BI P14_REGNUM))
    (clobber (reg:VNx16BI P15_REGNUM))]
   ""
-  "smstop\tsm"
+  {
+    return TARGET_SME ? "smstop\tsm" : ".inst 0xd503427f // smstop sm";
+  }
 )
 
 ;; -------------------------------------------------------------------------

diff --git a/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_1.c b/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_1.c
index 98922aaeae09bf31e5c11e175799e5e28d5cab6c..3a63da7439cce7bca22413d63324eb0b6945e4ac 100644 (file)
--- a/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_1.c
+++ b/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_1.c
@@ -1,5 +1,5 @@
 // { dg-options "-O -fomit-frame-pointer -fno-optimize-sibling-calls -funwind-tables" }
-// { dg-final { check-function-bodies "**" "" } }
+// { dg-final { check-function-bodies "**" "" "" { target "*-*-*" } {\t\.inst} } }
 
 void ns_callee ();
  void s_callee () [[arm::streaming]];
@@ -218,7 +218,7 @@ sc_caller_x1 (int *ptr, int a) [[arm::streaming_compatible]]
 **     bl      ns_callee_stack
 **     ldr     x16, \[x29, #?16\]
 **     tbz     x16, 0, .*
-**     smstart sm
+**     .inst 0xd503437f // smstart sm
 **     ...
 */
 void

diff --git a/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_11.c b/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_11.c
index ee6f98737d96d3da3645ac658c52e3b0fa988d2b..c72d03f33b971e0cdc299ef1795abd60c33b72a6 100644 (file)
--- a/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_11.c
+++ b/gcc/testsuite/gcc.target/aarch64/sme/call_sm_switch_11.c
@@ -1,5 +1,6 @@
 // { dg-options "-O -fomit-frame-pointer -fno-optimize-sibling-calls -funwind-tables -mtrack-speculation" }
-// { dg-final { check-function-bodies "**" "" } }
+// { dg-final { check-function-bodies "**" "" "" { target "*-*-*" } {\t\.inst} } }
+
 
 void ns_callee ();
  void s_callee () [[arm::streaming]];
@@ -196,7 +197,7 @@ sc_caller_x1 (int *ptr, int a) [[arm::streaming_compatible]]
 **     tst     x16, #?1
 **     beq     [^\n]*
 **     csel    x15, x15, xzr, ne
-**     smstart sm
+**     .inst 0xd503437f // smstart sm
 **     ...
 */
 void

diff --git a/gcc/testsuite/gcc.target/aarch64/sme/pr121028.c b/gcc/testsuite/gcc.target/aarch64/sme/pr121028.c
new file mode 100644 (file)
index 0000000..a6aa119
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sme/pr121028.c
@@ -0,0 +1,46 @@
+// PR121028
+// { dg-do assemble { target aarch64_asm_sme_ok } }
+// { dg-options "-O --save-temps" }
+// { dg-final { check-function-bodies "**" "" "" { target "*-*-*" } {\t\.inst} } }
+
+void ns_callee ();
+
+/*
+** sc_caller_sme:
+**     ...
+**     mrs     x16, svcr
+**     str     x16, \[x29, #?16\]
+**     ldr     x16, \[x29, #?16\]
+**     tbz     x16, 0, .*
+**     smstop  sm
+**     bl      ns_callee
+**     ldr     x16, \[x29, #?16\]
+**     tbz     x16, 0, .*
+**     smstart sm
+**     ...
+*/
+void sc_caller_sme() __arm_streaming_compatible
+{
+    ns_callee ();
+}
+
+#pragma GCC target "+nosme"
+
+/*
+** sc_caller_nosme:
+**     ...
+**     bl      __arm_sme_state
+**     str     x0, \[x29, #?16\]
+**     ldr     x16, \[x29, #?16\]
+**     tbz     x16, 0, .*
+**     .inst 0xd503427f // smstop sm
+**     bl      ns_callee
+**     ldr     x16, \[x29, #?16\]
+**     tbz     x16, 0, .*
+**     .inst 0xd503437f // smstart sm
+**     ...
+*/
+void sc_caller_nosme() __arm_streaming_compatible
+{
+    ns_callee ();
+}