nvptx: Support '-mfake-ptx-alloca': defer failure to run-time 'alloca' usage

Follow-up to commit 1146410c0feb0e82c689b1333fdf530a2b34dc2b
"nvptx: Support '-mfake-ptx-alloca'".  '-mfake-ptx-alloca' is applicable only
for configurations where PTX 'alloca' is not supported, where target libraries
are built with it enabled (that is, libstdc++, libgfortran).

This change progresses:

    [-FAIL:-]{+PASS:+} g++.dg/tree-ssa/pr20458.C  -std=gnu++17 (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} g++.dg/tree-ssa/pr20458.C  -std=gnu++17 [-compilation failed to produce executable-]{+execution test+}
    [-FAIL:-]{+PASS:+} g++.dg/tree-ssa/pr20458.C  -std=gnu++26 (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} g++.dg/tree-ssa/pr20458.C  -std=gnu++26 [-compilation failed to produce executable-]{+execution test+}
    UNSUPPORTED: g++.dg/tree-ssa/pr20458.C  -std=gnu++98: exception handling not supported

..., and "enables" a few test cases:

    FAIL: g++.old-deja/g++.other/sibcall1.C  -std=gnu++17 (test for excess errors)
    [Etc.]

    FAIL: g++.old-deja/g++.other/unchanging1.C  -std=gnu++17 (test for excess errors)
    [Etc.]

..., which now (unrelatedly to 'alloca', and in the same way as configurations
where PTX 'alloca' is supported) FAIL due to:

    unresolved symbol _Unwind_DeleteException
    collect2: error: ld returned 1 exit status

Most importantly, it progresses ~830 libstdc++ test cases:

    [-FAIL:-]{+PASS:+} [...] (test for excess errors)

..., with (if applicable, for most of them):

    [-UNRESOLVED:-]{+PASS:+} [...] [-compilation failed to produce executable-]{+execution test+}

..., or just a few 'FAIL: [...] execution test' where these test cases also
FAIL in configurations where PTX 'alloca' is supported, or ~120 instances of
'FAIL: [...]  execution test' due to run-time
'GCC/nvptx: sorry, unimplemented: dynamic stack allocation not supported'.

This change also resolves the cases noted in
commit bac2d8a246892334e24dfa7d62be0cd0648c5606
"nvptx: Build libgfortran with '-mfake-ptx-alloca' [PR107635]":

| With '-mfake-ptx-alloca', libgfortran again succeeds to build, and compared
| to before, we've got only a small number of regressions due to nvptx 'ld'
| complaining about 'unresolved symbol __GCC_nvptx__PTX_alloca_not_supported':
|
|     [-PASS:-]{+FAIL:+} gfortran.dg/coarray/codimension_2.f90 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)

    [-FAIL:-]{+PASS:+} gfortran.dg/coarray/codimension_2.f90 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)

|     [-PASS:-]{+FAIL:+} gfortran.dg/coarray/event_4.f08 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)
|     [-PASS:-]{+UNRESOLVED:+} gfortran.dg/coarray/event_4.f08 -fcoarray=lib  -O2  -lcaf_single [-execution test-]{+compilation failed to produce executable+}

    [-FAIL:-]{+PASS:+} gfortran.dg/coarray/event_4.f08 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} gfortran.dg/coarray/event_4.f08 -fcoarray=lib  -O2  -lcaf_single [-compilation failed to produce executable-]{+execution test+}

|     [-PASS:-]{+FAIL:+} gfortran.dg/coarray/fail_image_2.f08 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)
|     [-PASS:-]{+UNRESOLVED:+} gfortran.dg/coarray/fail_image_2.f08 -fcoarray=lib  -O2  -lcaf_single [-execution test-]{+compilation failed to produce executable+}

    [-FAIL:-]{+PASS:+} gfortran.dg/coarray/fail_image_2.f08 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} gfortran.dg/coarray/fail_image_2.f08 -fcoarray=lib  -O2  -lcaf_single [-compilation failed to produce executable-]{+execution test+}

|     [-PASS:-]{+FAIL:+} gfortran.dg/coarray/proc_pointer_assign_1.f90 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)
|     [-PASS:-]{+UNRESOLVED:+} gfortran.dg/coarray/proc_pointer_assign_1.f90 -fcoarray=lib  -O2  -lcaf_single [-execution test-]{+compilation failed to produce executable+}

    [-FAIL:-]{+PASS:+} gfortran.dg/coarray/proc_pointer_assign_1.f90 -fcoarray=lib  -O2  -lcaf_single (test for excess errors)
    [-UNRESOLVED:-]{+PASS:+} gfortran.dg/coarray/proc_pointer_assign_1.f90 -fcoarray=lib  -O2  -lcaf_single [-compilation failed to produce executable-]{+execution test+}

|     [-PASS:-]{+FAIL:+} gfortran.dg/coarray_43.f90   -O  (test for excess errors)

    [-FAIL:-]{+PASS:+} gfortran.dg/coarray_43.f90   -O  (test for excess errors)

..., and further progresses:

    [-FAIL:-]{+PASS:+} gfortran.dg/coarray_lib_comm_1.f90   -O0  (test for excess errors)
    [-UNRESOLVED:-]{+FAIL:+} gfortran.dg/coarray_lib_comm_1.f90   -O0  [-compilation failed to produce executable-]{+execution test+}
    [Etc.]

..., which now (unrelatedly to 'alloca', and in the same way as configurations
where PTX 'alloca' is supported) FAILs due to:

    error   : Prototype doesn't match for '_gfortran_caf_transfer_between_remotes' in 'input file 9 at offset 159897', first defined in 'input file 9 at offset 159897'
    error   : Prototype doesn't match for '_gfortran_caf_stop_numeric' in 'input file 9 at offset 159897', first defined in 'input file 9 at offset 159897'
    nvptx-run: cuLinkAddData failed: device kernel image is invalid (CUDA_ERROR_INVALID_SOURCE, 300)

	gcc/
	* config/nvptx/nvptx.opt (-mfake-ptx-alloca): Update.
	gcc/testsuite/
	* gcc.target/nvptx/alloca-2-O0_-mfake-ptx-alloca.c: Adjust.
	libgcc/
	* config/nvptx/alloca.c: New.
	* config/nvptx/t-nvptx (LIB2ADD): Add it.

2 files changed, 9 insertions, 8 deletions

diff --git a/gcc/config/nvptx/nvptx.opt b/gcc/config/nvptx/nvptx.opt
index 02d36b3..9be81ae 100644
--- a/gcc/config/nvptx/nvptx.opt
+++ b/gcc/config/nvptx/nvptx.opt
@@ -173,12 +173,12 @@ 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'.
+; in presence of dynamic stack allocation, with '-mfake-ptx-alloca' enabled,
+; compilation, assembly, and linking succeeds, as does execution, in case that
+; 'alloca' is not attempted (if only used in error code paths, for example),
+; and a run-time failure only in case that 'alloca' is actually attempted.
 ; 
 ; 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.
+; build to succeed, and error out just upon actual, very rare use of 'alloca'.
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
index 4cc4d0c..92562cd 100644
--- 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
@@ -1,4 +1,4 @@
-/* { dg-do link } */
+/* { dg-do run } */
 /* { dg-options {-O0 -mno-soft-stack} } */
 /* { dg-additional-options -march=sm_30 } */
 /* { dg-additional-options -mfake-ptx-alloca } */
@@ -13,6 +13,7 @@ main(void)
 
 /* { 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-bogus __GCC_nvptx__PTX_alloca_not_supported {unresolved symbol} { target *-*-* } 0 } */
 
-/* { dg-final output-exists-not } */
+/* { dg-output {GCC/nvptx: sorry, unimplemented: dynamic stack allocation not supported[\r\n]+} }
+   { dg-shouldfail __GCC_nvptx__PTX_alloca_not_supported } */