🐛 [BUG] - Not Generating AVX Instructions

[radelja]

💿 OS

Ubuntu 22

🏗️ Architecture

x86_64

📝 Description

The use of the #pragma omp simd OpenMP directive in Configuration.cc does not result in AVX instructions with the GNU C++ compiler on ADL and CSL, even when -O3 is specified (-DCMAKE_CXX_FLAGS="-O3").

To generate AVX instructions, I needed to pass the -mavx flag with -DCMAKE_CXX_FLAGS="-O3 -mavx" when building with CMake. The GNU C++ compiler will now generate VMOVSD instructions instead of MOVSD instructions in the Spatter kernels.

🔄 Reproduction steps

1. Go to project root directory
2. Run CMake to build OpenMP backend with cmake -DCMAKE_CXX_FLAGS="-O3" -DUSE_OPENMP=1 -B build_openmp -S . && make -j$(nproc) -C build_openmp
3. Disassemble a kernel with objdump --disassemble=_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0 ./build_openmp/spatter

💬 Logs

./build_openmp/spatter:     file format elf64-x86-64


Disassembly of section .init:

Disassembly of section .plt:

Disassembly of section .plt.got:

Disassembly of section .plt.sec:

Disassembly of section .text:

00000000000122f0 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0>:
   122f0:	f3 0f 1e fa          	endbr64 
   122f4:	41 55                	push   %r13
   122f6:	41 54                	push   %r12
   122f8:	55                   	push   %rbp
   122f9:	48 89 fd             	mov    %rdi,%rbp
   122fc:	53                   	push   %rbx
   122fd:	48 83 ec 08          	sub    $0x8,%rsp
   12301:	4c 8b 2f             	mov    (%rdi),%r13
   12304:	e8 07 4a ff ff       	call   6d10 <omp_get_thread_num@plt>
   12309:	49 8b 9d 28 01 00 00 	mov    0x128(%r13),%rbx
   12310:	48 85 db             	test   %rbx,%rbx
   12313:	0f 84 be 00 00 00    	je     123d7 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0+0xe7>
   12319:	41 89 c4             	mov    %eax,%r12d
   1231c:	e8 ff 4a ff ff       	call   6e20 <omp_get_num_threads@plt>
   12321:	31 d2                	xor    %edx,%edx
   12323:	49 63 cc             	movslq %r12d,%rcx
   12326:	48 63 f0             	movslq %eax,%rsi
   12329:	48 89 d8             	mov    %rbx,%rax
   1232c:	48 f7 f6             	div    %rsi
   1232f:	48 39 d1             	cmp    %rdx,%rcx
   12332:	0f 82 aa 00 00 00    	jb     123e2 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0+0xf2>
   12338:	48 89 c6             	mov    %rax,%rsi
   1233b:	48 0f af f1          	imul   %rcx,%rsi
   1233f:	4c 8d 14 16          	lea    (%rsi,%rdx,1),%r10
   12343:	4e 8d 1c 10          	lea    (%rax,%r10,1),%r11
   12347:	4d 39 da             	cmp    %r11,%r10
   1234a:	0f 83 87 00 00 00    	jae    123d7 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0+0xe7>
   12350:	49 8b 85 98 00 00 00 	mov    0x98(%r13),%rax
   12357:	49 8b 95 e8 00 00 00 	mov    0xe8(%r13),%rdx
   1235e:	48 8b 75 08          	mov    0x8(%rbp),%rsi
   12362:	49 8b 9d 20 01 00 00 	mov    0x120(%r13),%rbx
   12369:	4c 8b 00             	mov    (%rax),%r8
   1236c:	48 8d 04 49          	lea    (%rcx,%rcx,2),%rax
   12370:	48 8b 0a             	mov    (%rdx),%rcx
   12373:	49 8b ad 00 01 00 00 	mov    0x100(%r13),%rbp
   1237a:	48 8d 04 c1          	lea    (%rcx,%rax,8),%rax
   1237e:	4c 8b 20             	mov    (%rax),%r12
   12381:	48 85 f6             	test   %rsi,%rsi
   12384:	74 51                	je     123d7 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0+0xe7>
   12386:	4c 89 d1             	mov    %r10,%rcx
   12389:	4d 8b 4d 50          	mov    0x50(%r13),%r9
   1238d:	48 0f af cd          	imul   %rbp,%rcx
   12391:	0f 1f 80 00 00 00 00 	nopl   0x0(%rax)
   12398:	4c 89 d0             	mov    %r10,%rax
   1239b:	31 d2                	xor    %edx,%edx
   1239d:	48 f7 f3             	div    %rbx
   123a0:	31 c0                	xor    %eax,%eax
   123a2:	48 0f af d6          	imul   %rsi,%rdx
   123a6:	49 8d 3c d4          	lea    (%r12,%rdx,8),%rdi
   123aa:	66 0f 1f 44 00 00    	nopw   0x0(%rax,%rax,1)
   123b0:	49 8b 14 c1          	mov    (%r9,%rax,8),%rdx
   123b4:	f2 0f 10 04 c7       	movsd  (%rdi,%rax,8),%xmm0
   123b9:	48 83 c0 01          	add    $0x1,%rax
   123bd:	48 01 ca             	add    %rcx,%rdx
   123c0:	f2 41 0f 11 04 d0    	movsd  %xmm0,(%r8,%rdx,8)
   123c6:	48 39 c6             	cmp    %rax,%rsi
   123c9:	75 e5                	jne    123b0 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0+0xc0>
   123cb:	49 83 c2 01          	add    $0x1,%r10
   123cf:	48 01 e9             	add    %rbp,%rcx
   123d2:	4d 39 d3             	cmp    %r10,%r11
   123d5:	75 c1                	jne    12398 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0+0xa8>
   123d7:	48 83 c4 08          	add    $0x8,%rsp
   123db:	5b                   	pop    %rbx
   123dc:	5d                   	pop    %rbp
   123dd:	41 5c                	pop    %r12
   123df:	41 5d                	pop    %r13
   123e1:	c3                   	ret    
   123e2:	48 83 c0 01          	add    $0x1,%rax
   123e6:	31 d2                	xor    %edx,%edx
   123e8:	e9 4b ff ff ff       	jmp    12338 <_ZN7Spatter13ConfigurationINS_6OpenMPEE7scatterEbm._omp_fn.0+0x48>

Disassembly of section .fini: