Turn off gsframe option if GCC supports it (#1037)

Recent versions of GCC (15.2.0, possibly slightly earlier too)
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.

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

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

Author: mhucka

Makefile

@@ -46,6 +46,19 @@ 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 $(CXX) -Wa,--gsframe=no -c -x c++ /dev/null \
+    -o /dev/null 2>/dev/null && echo "true")
+ifeq ($(SUPPORTS_GSFRAME),true)
+    CXXFLAGS += -Wa,--gsframe=no
+    NVCCFLAGS += -Xcompiler -Wa,--gsframe=no
+    HIPCCFLAGS += -Wa,--gsframe=no
+endif
+
 LTO_FLAGS := -flto=auto
 USING_CLANG := $(shell $(CXX) --version | grep -isq clang && echo "true")
 ifeq ($(USING_CLANG),true)
@@ -126,7 +139,7 @@ ifneq (,$(strip $(CUQUANTUM_ROOT)))
     endif
 endif
 
-# Export all variables to subprocesses without having to export them individually.
+# Export all vars to subprocesses without having to export them individually.
 .EXPORT_ALL_VARIABLES:
 
 # The rest is build rules and make targets.
@@ -214,7 +227,7 @@ run-tests tests: $(TESTS)
 .PHONY: check-cuquantum-root-set
 check-cuquantum-root-set:
 	@if test -z "$(CUQUANTUM_ROOT)"; then \
-	    echo Error: '$$CUQUANTUM_ROOT must be set in order to use cuStateVec.'; \
+	    echo Error: 'Must set $$CUQUANTUM_ROOT to use cuStateVec.'; \
 	    exit 1; \
 	fi
 
@@ -241,7 +254,7 @@ 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);)

tests/Makefile

@@ -40,7 +40,7 @@ endif
 
 CXX_FILES := $(BASIC_FILES) $(SSE_FILES) $(AVX2_FILES) $(AVX512_FILES)
 CXX_TARGETS := $(CXX_FILES:%.cc=%.x)
-CXXFLAGS := $(CXXFLAGS) $(SSE_FLAGS) $(AVX2_FLAGS) $(AVX512_FLAGS) $(BMI2_FLAGS)
+CXXFLAGS += $(SSE_FLAGS) $(AVX2_FLAGS) $(AVX512_FLAGS) $(BMI2_FLAGS)
 
 CUDA_FILES := $(wildcard *cuda_test.cu)
 CUDA_TARGETS := $(CUDA_FILES:%cuda_test.cu=%cuda_test.x)