https://gcc.gnu.org/g:1146410c0feb0e82c689b1333fdf530a2b34dc2b
commit r15-7735-g1146410c0feb0e82c689b1333fdf530a2b34dc2b
Author: Thomas Schwinge <tschwi...@baylibre.com>
Date: Mon Feb 24 16:13:11 2025 +0100
nvptx: Support '-mfake-ptx-alloca'
With '-mfake-ptx-alloca' enabled, the user-visible behavior changes only
for configurations where PTX 'alloca' is not available. Rather than a
compile-time 'sorry, unimplemented: dynamic stack allocation not supported'
in presence of dynamic stack allocation, compilation and assembly then
succeeds. However, attempting to link in such '*.o' files then fails due
to unresolved symbol '__GCC_nvptx__PTX_alloca_not_supported'.
This is meant to be used in scenarios where large volumes of code are
compiled, a small fraction of which runs into dynamic stack allocation, but
these parts are not important for specific use cases, and we'd thus like the
build to succeed, and error out just upon actual, very rare use of the
offending '*.o' files.
gcc/
* config/nvptx/nvptx.opt (-mfake-ptx-alloca): New.
* config/nvptx/nvptx-protos.h (nvptx_output_fake_ptx_alloca):
Declare.
* config/nvptx/nvptx.cc (nvptx_output_fake_ptx_alloca): New.
* config/nvptx/nvptx.md (define_insn "@nvptx_alloca_<mode>")
[!(TARGET_PTX_7_3 && TARGET_SM52)]: Use it for
'-mfake-ptx-alloca'.
gcc/testsuite/
* gcc.target/nvptx/alloca-1-O0_-mfake-ptx-alloca.c: New.
* gcc.target/nvptx/alloca-2-O0_-mfake-ptx-alloca.c: Likewise.
* gcc.target/nvptx/alloca-4-O3_-mfake-ptx-alloca.c: Likewise.
* gcc.target/nvptx/vla-1-O0_-mfake-ptx-alloca.c: Likewise.
* gcc.target/nvptx/alloca-4-O3.c:
'dg-additional-options -mfake-ptx-alloca'.
Diff:
---
gcc/config/nvptx/nvptx-protos.h | 1 +
gcc/config/nvptx/nvptx.cc | 21 ++++++++++
gcc/config/nvptx/nvptx.md | 4 ++
gcc/config/nvptx/nvptx.opt | 15 +++++++
.../nvptx/alloca-1-O0_-mfake-ptx-alloca.c | 49 ++++++++++++++++++++++
.../nvptx/alloca-2-O0_-mfake-ptx-alloca.c | 18 ++++++++
gcc/testsuite/gcc.target/nvptx/alloca-4-O3.c | 2 +
.../nvptx/alloca-4-O3_-mfake-ptx-alloca.c | 48 +++++++++++++++++++++
.../gcc.target/nvptx/vla-1-O0_-mfake-ptx-alloca.c | 29 +++++++++++++
9 files changed, 187 insertions(+)
diff --git a/gcc/config/nvptx/nvptx-protos.h b/gcc/config/nvptx/nvptx-protos.h
index e85e758322d7..ca1fed6d9920 100644
--- a/gcc/config/nvptx/nvptx-protos.h
+++ b/gcc/config/nvptx/nvptx-protos.h
@@ -55,6 +55,7 @@ extern rtx nvptx_expand_compare (rtx);
extern const char *nvptx_ptx_type_from_mode (machine_mode, bool);
extern const char *nvptx_output_mov_insn (rtx, rtx);
extern const char *nvptx_output_call_insn (rtx_insn *, rtx, rtx);
+extern const char *nvptx_output_fake_ptx_alloca (void);
extern const char *nvptx_output_return (void);
extern const char *nvptx_output_set_softstack (unsigned);
extern const char *nvptx_output_simt_enter (rtx, rtx, rtx);
diff --git a/gcc/config/nvptx/nvptx.cc b/gcc/config/nvptx/nvptx.cc
index 64de2b1cc9be..d1648d52f2fa 100644
--- a/gcc/config/nvptx/nvptx.cc
+++ b/gcc/config/nvptx/nvptx.cc
@@ -1758,6 +1758,27 @@ nvptx_output_set_softstack (unsigned src_regno)
}
return "";
}
+
+/* Output a fake PTX 'alloca'. */
+
+const char *
+nvptx_output_fake_ptx_alloca (void)
+{
+#define FAKE_PTX_ALLOCA_NAME "__GCC_nvptx__PTX_alloca_not_supported"
+ static tree decl;
+ if (!decl)
+ {
+ tree alloca_type = TREE_TYPE (builtin_decl_explicit (BUILT_IN_ALLOCA));
+ decl = build_decl (UNKNOWN_LOCATION, FUNCTION_DECL,
+ get_identifier (FAKE_PTX_ALLOCA_NAME), alloca_type);
+ DECL_EXTERNAL (decl) = 1;
+ TREE_PUBLIC (decl) = 1;
+ nvptx_record_needed_fndecl (decl);
+ }
+ return "\tcall\t(%0), " FAKE_PTX_ALLOCA_NAME ", (%1);";
+#undef FAKE_PTX_ALLOCA_NAME
+}
+
/* Output a return instruction. Also copy the return value to its outgoing
location. */
diff --git a/gcc/config/nvptx/nvptx.md b/gcc/config/nvptx/nvptx.md
index d08afd4378bf..3201247c5fb1 100644
--- a/gcc/config/nvptx/nvptx.md
+++ b/gcc/config/nvptx/nvptx.md
@@ -1705,6 +1705,8 @@
output_asm_insn ("}", NULL);
return "";
}
+ else if (nvptx_fake_ptx_alloca)
+ return nvptx_output_fake_ptx_alloca ();
else
{
sorry_at (INSN_LOCATION (insn),
@@ -1733,6 +1735,7 @@
gcc_checking_assert (REG_P (operands[0]));
emit_insn (gen_nvptx_stacksave (Pmode, operands[0], operands[1]));
}
+ /* We don't bother to special-case '-mfake-ptx-alloca' here. */
else
{
/* The concept of a '%stack' pointer doesn't apply like this.
@@ -1765,6 +1768,7 @@
operands[1] = force_reg (Pmode, operands[1]);
emit_insn (gen_nvptx_stackrestore (Pmode, operands[0], operands[1]));
}
+ /* We don't bother to special-case '-mfake-ptx-alloca' here. */
else if (!TARGET_SOFT_STACK)
; /* See 'save_stack_block'. */
else if (TARGET_SOFT_STACK)
diff --git a/gcc/config/nvptx/nvptx.opt b/gcc/config/nvptx/nvptx.opt
index 273d366d35e6..02d36b33025b 100644
--- a/gcc/config/nvptx/nvptx.opt
+++ b/gcc/config/nvptx/nvptx.opt
@@ -167,3 +167,18 @@ Target Var(nvptx_alias) Init(0) Undocumented
mexperimental
Target Var(nvptx_experimental) Init(0) Undocumented
+
+mfake-ptx-alloca
+Target Var(nvptx_fake_ptx_alloca) Init(0) Undocumented
+; With '-mfake-ptx-alloca' enabled, the user-visible behavior changes only
+; for configurations where PTX 'alloca' is not available. Rather than a
+; compile-time 'sorry, unimplemented: dynamic stack allocation not supported'
+; in presence of dynamic stack allocation, compilation and assembly then
+; succeeds. However, attempting to link in such '*.o' files then fails due
+; to unresolved symbol '__GCC_nvptx__PTX_alloca_not_supported'.
+;
+; This is meant to be used in scenarios where large volumes of code are
+; compiled, a small fraction of which runs into dynamic stack allocation, but
+; these parts are not important for specific use cases, and we'd thus like the
+; build to succeed, and error out just upon actual, very rare use of the
+; offending '*.o' files.
diff --git a/gcc/testsuite/gcc.target/nvptx/alloca-1-O0_-mfake-ptx-alloca.c
b/gcc/testsuite/gcc.target/nvptx/alloca-1-O0_-mfake-ptx-alloca.c
new file mode 100644
index 000000000000..7c405592e693
--- /dev/null
+++ b/gcc/testsuite/gcc.target/nvptx/alloca-1-O0_-mfake-ptx-alloca.c
@@ -0,0 +1,49 @@
+/* { dg-do assemble } */
+/* { dg-options {-O0 -mno-soft-stack} } */
+/* { dg-additional-options -march=sm_30 } */
+/* { dg-additional-options -mfake-ptx-alloca } */
+/* { dg-additional-options -save-temps } */
+/* { dg-final { check-function-bodies {** } {} } } */
+
+void sink(void *);
+
+void f(void)
+{
+ sink(__builtin_alloca(123));
+ /* { dg-bogus {sorry, unimplemented: dynamic stack allocation not supported}
{} { target *-*-* } .-1 } */
+}
+/*
+** f:
+** \.visible \.func f
+** {
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** mov\.u64 \11, 16;
+** add\.u64 \2, \11, -1;
+** add\.u64 \3, \2, 123;
+** div\.u64 \4, \3, 16;
+** mul\.lo\.u64 \5, \4, 16;
+** call \(\6\), __GCC_nvptx__PTX_alloca_not_supported, \(\5\);
+** add\.u64 \7, \6, 15;
+** shr\.u64 \8, \7, 4;
+** shl\.b64 \9, \8, 4;
+** mov\.u64 \1, \9;
+** mov\.u64 \10, \1;
+** {
+** \.param\.u64 %out_arg1;
+** st\.param\.u64 \[%out_arg1\], \10;
+** call sink, \(%out_arg1\);
+** }
+** ret;
+*/
+
+/* { dg-final { scan-assembler-times {(?n)^\.extern \.func \(\.param\.u64
%value_out\) __GCC_nvptx__PTX_alloca_not_supported \(\.param\.u64 %in_ar0\);$}
1 } } */
diff --git a/gcc/testsuite/gcc.target/nvptx/alloca-2-O0_-mfake-ptx-alloca.c
b/gcc/testsuite/gcc.target/nvptx/alloca-2-O0_-mfake-ptx-alloca.c
new file mode 100644
index 000000000000..4cc4d0c93f28
--- /dev/null
+++ b/gcc/testsuite/gcc.target/nvptx/alloca-2-O0_-mfake-ptx-alloca.c
@@ -0,0 +1,18 @@
+/* { dg-do link } */
+/* { dg-options {-O0 -mno-soft-stack} } */
+/* { dg-additional-options -march=sm_30 } */
+/* { dg-additional-options -mfake-ptx-alloca } */
+/* { dg-additional-options -save-temps } */
+
+int
+main(void)
+{
+ return !(__builtin_alloca(100) != __builtin_alloca(10));
+}
+/* { dg-final { scan-assembler-times {(?n)\tcall\t\(%r[0-9]+\),
__GCC_nvptx__PTX_alloca_not_supported, \(%r[0-9]+\);$} 2 } } */
+
+/* { dg-final { scan-assembler-times {(?n)^\.extern \.func \(\.param\.u64
%value_out\) __GCC_nvptx__PTX_alloca_not_supported \(\.param\.u64 %in_ar0\);$}
1 } } */
+
+/* { dg-message __GCC_nvptx__PTX_alloca_not_supported {unresolved symbol} {
target *-*-* } 0 } */
+
+/* { dg-final output-exists-not } */
diff --git a/gcc/testsuite/gcc.target/nvptx/alloca-4-O3.c
b/gcc/testsuite/gcc.target/nvptx/alloca-4-O3.c
index df1320ea2642..4374bb54ab37 100644
--- a/gcc/testsuite/gcc.target/nvptx/alloca-4-O3.c
+++ b/gcc/testsuite/gcc.target/nvptx/alloca-4-O3.c
@@ -1,6 +1,8 @@
/* { dg-do assemble } */
/* { dg-options {-O3 -mno-soft-stack} } */
/* { dg-add-options nvptx_alloca_ptx } */
+/* Verify the fake one isn't used if the real PTX 'alloca' is available.
+ { dg-additional-options -mfake-ptx-alloca } */
/* { dg-additional-options -save-temps } */
/* { dg-final { check-function-bodies {** } {} } } */
diff --git a/gcc/testsuite/gcc.target/nvptx/alloca-4-O3_-mfake-ptx-alloca.c
b/gcc/testsuite/gcc.target/nvptx/alloca-4-O3_-mfake-ptx-alloca.c
new file mode 100644
index 000000000000..e394763f01b4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/nvptx/alloca-4-O3_-mfake-ptx-alloca.c
@@ -0,0 +1,48 @@
+/* { dg-do assemble } */
+/* { dg-options {-O3 -mno-soft-stack} } */
+/* { dg-additional-options {-march=sm_30 -mfake-ptx-alloca} } */
+/* { dg-additional-options -save-temps } */
+/* { dg-final { check-function-bodies {** } {} } } */
+
+void sink(void *);
+
+void f(void)
+{
+ void *p;
+ p = __builtin_stack_save();
+ sink(__builtin_alloca(25));
+ /* { dg-bogus {sorry, unimplemented: dynamic stack allocation not supported}
{} { target *-*-* } .-1 } */
+ __builtin_stack_restore(p);
+ sink(__builtin_alloca(13));
+ /* { dg-bogus {sorry, unimplemented: dynamic stack allocation not supported}
{} { target *-*-* } .-1 } */
+}
+/*
+** f:
+** .visible .func f
+** {
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** \.reg\.u64 (%r[0-9]+);
+** call \(\1\), __GCC_nvptx__PTX_alloca_not_supported, \(32\);
+** add\.u64 \2, \1, 15;
+** and\.b64 \3, \2, -16;
+** {
+** \.param\.u64 %out_arg1;
+** st\.param\.u64 \[%out_arg1\], \3;
+** call sink, \(%out_arg1\);
+** }
+** call \(\4\), __GCC_nvptx__PTX_alloca_not_supported, \(16\);
+** add\.u64 \5, \4, 15;
+** and\.b64 \6, \5, -16;
+** {
+** \.param\.u64 %out_arg1;
+** st\.param\.u64 \[%out_arg1\], \6;
+** call sink, \(%out_arg1\);
+** }
+** ret;
+*/
+
+/* { dg-final { scan-assembler-times {(?n)^\.extern \.func \(\.param\.u64
%value_out\) __GCC_nvptx__PTX_alloca_not_supported \(\.param\.u64 %in_ar0\);$}
1 } } */
diff --git a/gcc/testsuite/gcc.target/nvptx/vla-1-O0_-mfake-ptx-alloca.c
b/gcc/testsuite/gcc.target/nvptx/vla-1-O0_-mfake-ptx-alloca.c
new file mode 100644
index 000000000000..3e5134ae3807
--- /dev/null
+++ b/gcc/testsuite/gcc.target/nvptx/vla-1-O0_-mfake-ptx-alloca.c
@@ -0,0 +1,29 @@
+/* { dg-do assemble } */
+/* { dg-options {-O0 -mno-soft-stack} } */
+/* { dg-additional-options -march=sm_30 } */
+/* { dg-additional-options -mfake-ptx-alloca } */
+/* { dg-additional-options -save-temps } */
+/* { dg-final { check-function-bodies {** } {} } } */
+
+void sink(void *);
+
+void f(int s)
+{
+ char a[s];
+ /* { dg-bogus {sorry, unimplemented: dynamic stack allocation not supported}
{} { target *-*-* } .-1 } */
+ sink(a);
+}
+/*
+** f:
+** ...
+** cvt\.s64\.s32 (%r[0-9]+), (%r[0-9]+);
+** mov\.u64 (%r[0-9]+), 16;
+** add\.u64 (%r[0-9]+), \3, -1;
+** add\.u64 (%r[0-9]+), \1, \4;
+** div\.u64 (%r[0-9]+), \5, 16;
+** mul\.lo\.u64 (%r[0-9]+), \6, 16;
+** call \((%r[0-9]+)\), __GCC_nvptx__PTX_alloca_not_supported,
\(\7\);
+** ...
+*/
+
+/* { dg-final { scan-assembler-times {(?n)^\.extern \.func \(\.param\.u64
%value_out\) __GCC_nvptx__PTX_alloca_not_supported \(\.param\.u64 %in_ar0\);$}
1 } } */
