From aec51564a55375e7fcf52bfccef226381f220bb5 Mon Sep 17 00:00:00 2001 From: Oli Scherer Date: Wed, 8 Jan 2025 14:21:40 +0000 Subject: [PATCH 1/4] Add regression test for option initialization --- tests/codegen/slice-init.rs | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/tests/codegen/slice-init.rs b/tests/codegen/slice-init.rs index 8126bf84618aa..a01b432add63a 100644 --- a/tests/codegen/slice-init.rs +++ b/tests/codegen/slice-init.rs @@ -63,6 +63,34 @@ pub fn nonzero_integer_array() { opaque(&x); } +const N: usize = 100; + +// FIXME: The two bytes of the u16 are the same, so we should +// just use memset, too. +// CHECK-LABEL: @u16_init_one_bytes +#[no_mangle] +pub fn u16_init_one_bytes() -> [u16; N] { + // CHECK-NOT: select + // CHECK: br + // CHECK-NOT: switch + // CHECK: icmp + // CHECK-NOT: call void @llvm.memset.p0 + [const { u16::from_be_bytes([1, 1]) }; N] +} + +// FIXME: undef bytes can just be initialized with the same value as the +// defined bytes, if the defines bytes are all the same. +// CHECK-LABEL: @option_none_init +#[no_mangle] +pub fn option_none_init() -> [Option; N] { + // CHECK-NOT: select + // CHECK: br label %repeat_loop_header{{.*}} + // CHECK-NOT: switch + // CHECK: icmp + // CHECK-NOT: call void @llvm.memset.p0 + [None; N] +} + // Use an opaque function to prevent rustc from removing useless drops. #[inline(never)] pub fn opaque(_: impl Sized) {} From 7ad45f1d2fc5b237a0f3ce128dc403eb6f618403 Mon Sep 17 00:00:00 2001 From: Oli Scherer Date: Wed, 8 Jan 2025 15:00:25 +0000 Subject: [PATCH 2/4] Change repeat element check into a match --- compiler/rustc_codegen_ssa/src/mir/rvalue.rs | 33 +++++++++++--------- 1 file changed, 18 insertions(+), 15 deletions(-) diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs index 3b62148abb789..8ef25d4e2ffb5 100644 --- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs +++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs @@ -93,23 +93,26 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { return; } - if let OperandValue::Immediate(v) = cg_elem.val { - let start = dest.val.llval; - let size = bx.const_usize(dest.layout.size.bytes()); - - // Use llvm.memset.p0i8.* to initialize all zero arrays - if bx.cx().const_to_opt_u128(v, false) == Some(0) { - let fill = bx.cx().const_u8(0); - bx.memset(start, fill, size, dest.val.align, MemFlags::empty()); - return; - } + match cg_elem.val { + OperandValue::Immediate(v) => { + let start = dest.val.llval; + let size = bx.const_usize(dest.layout.size.bytes()); + + // Use llvm.memset.p0i8.* to initialize all zero arrays + if bx.cx().const_to_opt_u128(v, false) == Some(0) { + let fill = bx.cx().const_u8(0); + bx.memset(start, fill, size, dest.val.align, MemFlags::empty()); + return; + } - // Use llvm.memset.p0i8.* to initialize byte arrays - let v = bx.from_immediate(v); - if bx.cx().val_ty(v) == bx.cx().type_i8() { - bx.memset(start, v, size, dest.val.align, MemFlags::empty()); - return; + // Use llvm.memset.p0i8.* to initialize byte arrays + let v = bx.from_immediate(v); + if bx.cx().val_ty(v) == bx.cx().type_i8() { + bx.memset(start, v, size, dest.val.align, MemFlags::empty()); + return; + } } + _ => (), } let count = self From 65ea9f3eb40e113284d0142f28e061fd90191c46 Mon Sep 17 00:00:00 2001 From: Oli Scherer Date: Wed, 8 Jan 2025 16:15:50 +0000 Subject: [PATCH 3/4] Pull element init into a reusable closure --- compiler/rustc_codegen_ssa/src/mir/rvalue.rs | 35 ++++++++++++-------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs index 8ef25d4e2ffb5..e36e0e18d9ccd 100644 --- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs +++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs @@ -93,22 +93,29 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { return; } - match cg_elem.val { - OperandValue::Immediate(v) => { - let start = dest.val.llval; - let size = bx.const_usize(dest.layout.size.bytes()); + let try_init_all_same = |bx: &mut Bx, v| { + let start = dest.val.llval; + let size = bx.const_usize(dest.layout.size.bytes()); + + // Use llvm.memset.p0i8.* to initialize all zero arrays + if bx.cx().const_to_opt_u128(v, false) == Some(0) { + let fill = bx.cx().const_u8(0); + bx.memset(start, fill, size, dest.val.align, MemFlags::empty()); + return true; + } - // Use llvm.memset.p0i8.* to initialize all zero arrays - if bx.cx().const_to_opt_u128(v, false) == Some(0) { - let fill = bx.cx().const_u8(0); - bx.memset(start, fill, size, dest.val.align, MemFlags::empty()); - return; - } + // Use llvm.memset.p0i8.* to initialize byte arrays + let v = bx.from_immediate(v); + if bx.cx().val_ty(v) == bx.cx().type_i8() { + bx.memset(start, v, size, dest.val.align, MemFlags::empty()); + return true; + } + false + }; - // Use llvm.memset.p0i8.* to initialize byte arrays - let v = bx.from_immediate(v); - if bx.cx().val_ty(v) == bx.cx().type_i8() { - bx.memset(start, v, size, dest.val.align, MemFlags::empty()); + match cg_elem.val { + OperandValue::Immediate(v) => { + if try_init_all_same(bx, v) { return; } } From 65b01cb1823926fd4e2f2c94b206aad0220c0e1c Mon Sep 17 00:00:00 2001 From: Oli Scherer Date: Wed, 8 Jan 2025 16:29:32 +0000 Subject: [PATCH 4/4] Use llvm.memset.p0i8.* to initialize all same-bytes arrays --- compiler/rustc_codegen_ssa/src/mir/rvalue.rs | 14 +++++++++----- tests/codegen/slice-init.rs | 8 +++----- 2 files changed, 12 insertions(+), 10 deletions(-) diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs index e36e0e18d9ccd..31793641d75ed 100644 --- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs +++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs @@ -97,11 +97,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> { let start = dest.val.llval; let size = bx.const_usize(dest.layout.size.bytes()); - // Use llvm.memset.p0i8.* to initialize all zero arrays - if bx.cx().const_to_opt_u128(v, false) == Some(0) { - let fill = bx.cx().const_u8(0); - bx.memset(start, fill, size, dest.val.align, MemFlags::empty()); - return true; + // Use llvm.memset.p0i8.* to initialize all same byte arrays + if let Some(int) = bx.cx().const_to_opt_u128(v, false) { + let bytes = &int.to_le_bytes()[..cg_elem.layout.size.bytes_usize()]; + let first = bytes[0]; + if bytes[1..].iter().all(|&b| b == first) { + let fill = bx.cx().const_u8(first); + bx.memset(start, fill, size, dest.val.align, MemFlags::empty()); + return true; + } } // Use llvm.memset.p0i8.* to initialize byte arrays diff --git a/tests/codegen/slice-init.rs b/tests/codegen/slice-init.rs index a01b432add63a..1c2dd3e887555 100644 --- a/tests/codegen/slice-init.rs +++ b/tests/codegen/slice-init.rs @@ -65,16 +65,14 @@ pub fn nonzero_integer_array() { const N: usize = 100; -// FIXME: The two bytes of the u16 are the same, so we should -// just use memset, too. // CHECK-LABEL: @u16_init_one_bytes #[no_mangle] pub fn u16_init_one_bytes() -> [u16; N] { // CHECK-NOT: select - // CHECK: br + // CHECK-NOT: br // CHECK-NOT: switch - // CHECK: icmp - // CHECK-NOT: call void @llvm.memset.p0 + // CHECK-NOT: icmp + // CHECK: call void @llvm.memset.p0 [const { u16::from_be_bytes([1, 1]) }; N] }