Turn off gsframe option if GCC supports it

Recent versions of GCC apparently introduced a new format (SFrame) for
fast stack unwinding by default or when certain flags are present. The
SFrame implementation seems to have a limitation in that it only
supports a subset of x86_64 registers for the Canonical Frame Address
(CFA):. qsim makes heavy use of AVX/AVX2/AVX512 instructions. When GCC
optimizes this code, it often uses additional registers to calculate the
stack frame. Since SFrame doesn't support these registers, the assembler
warns that it cannot emit SFrame data for those sections.

These warnings are harmless for qsim because it does not rely on SFrame
for its functionality. However, compilation produces _a lot_ of warning
messages, which is alarming and confusing.

This change adds the option `-Wa,--gsframe=no` to GCC if it supports the
option. This silences the warnings.

Author: mhucka

Makefile

@@ -46,6 +46,16 @@ CXXFLAGS := $(BASE_CXXFLAGS) $(CXXFLAGS)
 NVCCFLAGS := $(BASE_NVCCFLAGS) $(NVCCFLAGS)
 HIPCCFLAGS := $(BASE_HIPCCFLAGS) $(HIPCCFLAGS)
 
+# GCC 15 and Binutils 2.45+ generate SFrame stack unwinding info. The current
+# SFrame only supports a subset of x86_64 registers. When GCC optimizes AVX*
+# instructions, it uses additional registers, and that causes the assembler to
+# produce (many) warnings. They are harmless for qsim because it does not rely
+# on SFrame. Silence those warnings if the assembler supports it.
+SUPPORTS_GSFRAME := $(shell as --help 2>&1 | grep -isq "\-\-gsframe" && echo "true")
+ifeq ($(SUPPORTS_GSFRAME),true)
+    CXXFLAGS += -Wa,--gsframe=no
+endif
+
 LTO_FLAGS := -flto=auto
 USING_CLANG := $(shell $(CXX) --version | grep -isq clang && echo "true")
 ifeq ($(USING_CLANG),true)
@@ -241,7 +251,7 @@ clean:
 	-$(MAKE) -C pybind_interface/ clean
 
 LOCAL_VARS = TARGETS TESTS PYTESTS PYTESTFLAGS CXX CXXFLAGS NVCC NVCCFLAGS $\
-	HIPCC HIPCCFLAGS CUDA_PATH CUQUANTUM_ROOT CUSTATEVECFLAGS
+	HIPCC HIPCCFLAGS CUDA_PATH CUQUANTUM_ROOT CUSTATEVECFLAGS SUPPORTS_GSFRAME
 
 .PHONY: print-vars
 print-vars: ; @$(foreach n,$(sort $(LOCAL_VARS)),echo $n=$($n);)