[WebAssembly] Restore defaults for stores per memop

Summary:
Large slowdowns were observed in Rust due to many small, constant
sized copies in conjunction with poorly-optimized memory.copy
implementations. Since memory.copy cannot be expected to be inlined
efficiently by engines at this time, stop using it for the smallest
copies. We continue to lower all memcpy intrinsics to memory.copy,
though.

Reviewers: aheejin, alexcrichton

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, JDevlieghere, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67639

llvm-svn: 372275

llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp

@@ -259,16 +259,6 @@ WebAssemblyTargetLowering::WebAssemblyTargetLowering(
 
   setMaxAtomicSizeInBitsSupported(64);
 
-  if (Subtarget->hasBulkMemory()) {
-    // Use memory.copy and friends over multiple loads and stores
-    MaxStoresPerMemcpy = 1;
-    MaxStoresPerMemcpyOptSize = 1;
-    MaxStoresPerMemmove = 1;
-    MaxStoresPerMemmoveOptSize = 1;
-    MaxStoresPerMemset = 1;
-    MaxStoresPerMemsetOptSize = 1;
-  }
-
   // Override the __gnu_f2h_ieee/__gnu_h2f_ieee names so that the f32 name is
   // consistent with the f64 and f128 names.
   setLibcallName(RTLIB::FPEXT_F16_F32, "__extendhfsf2");

llvm/test/CodeGen/WebAssembly/bulk-memory.ll

@@ -142,8 +142,8 @@ define void @memset_1024(i8* %dest, i8 %val) {
 }
 
 ; The following tests check that frame index elimination works for
-; bulk memory instructions. The stack pointer is bumped by 16 instead
-; of 10 because the stack pointer in WebAssembly is currently always
+; bulk memory instructions. The stack pointer is bumped by 112 instead
+; of 100 because the stack pointer in WebAssembly is currently always
 ; 16-byte aligned, even in leaf functions, although it is not written
 ; back to the global in this case.
 
@@ -156,52 +156,52 @@ define void @memset_1024(i8* %dest, i8 %val) {
 ; NO-BULK-MEM-NOT: memory.copy
 ; BULK-MEM-NEXT: .functype memcpy_alloca_src (i32) -> ()
 ; BULK-MEM-NEXT: global.get $push[[L0:[0-9]+]]=, __stack_pointer
-; BULK-MEM-NEXT: i32.const $push[[L1:[0-9]+]]=, 16
+; BULK-MEM-NEXT: i32.const $push[[L1:[0-9]+]]=, 112
 ; BULK-MEM-NEXT: i32.sub $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]
-; BULK-MEM-NEXT: i32.const $push[[L3:[0-9]+]]=, 6
+; BULK-MEM-NEXT: i32.const $push[[L3:[0-9]+]]=, 12
 ; BULK-MEM-NEXT: i32.add $push[[L4:[0-9]+]]=, $pop[[L2]], $pop[[L3]]
-; BULK-MEM-NEXT: i32.const $push[[L5:[0-9]+]]=, 10
+; BULK-MEM-NEXT: i32.const $push[[L5:[0-9]+]]=, 100
 ; BULK-MEM-NEXT: memory.copy 0, 0, $0, $pop[[L4]], $pop[[L5]]
 ; BULK-MEM-NEXT: return
 define void @memcpy_alloca_src(i8* %dst) {
-  %a = alloca [10 x i8]
-  %p = bitcast [10 x i8]* %a to i8*
-  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %p, i32 10, i1 false)
+  %a = alloca [100 x i8]
+  %p = bitcast [100 x i8]* %a to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %p, i32 100, i1 false)
   ret void
 }
 
 ; CHECK-LABEL: memcpy_alloca_dst:
 ; NO-BULK-MEM-NOT: memory.copy
 ; BULK-MEM-NEXT: .functype memcpy_alloca_dst (i32) -> ()
 ; BULK-MEM-NEXT: global.get $push[[L0:[0-9]+]]=, __stack_pointer
-; BULK-MEM-NEXT: i32.const $push[[L1:[0-9]+]]=, 16
+; BULK-MEM-NEXT: i32.const $push[[L1:[0-9]+]]=, 112
 ; BULK-MEM-NEXT: i32.sub $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]
-; BULK-MEM-NEXT: i32.const $push[[L3:[0-9]+]]=, 6
+; BULK-MEM-NEXT: i32.const $push[[L3:[0-9]+]]=, 12
 ; BULK-MEM-NEXT: i32.add $push[[L4:[0-9]+]]=, $pop[[L2]], $pop[[L3]]
-; BULK-MEM-NEXT: i32.const $push[[L5:[0-9]+]]=, 10
+; BULK-MEM-NEXT: i32.const $push[[L5:[0-9]+]]=, 100
 ; BULK-MEM-NEXT: memory.copy 0, 0, $pop[[L4]], $0, $pop[[L5]]
 ; BULK-MEM-NEXT: return
 define void @memcpy_alloca_dst(i8* %src) {
-  %a = alloca [10 x i8]
-  %p = bitcast [10 x i8]* %a to i8*
-  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %p, i8* %src, i32 10, i1 false)
+  %a = alloca [100 x i8]
+  %p = bitcast [100 x i8]* %a to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %p, i8* %src, i32 100, i1 false)
   ret void
 }
 
 ; CHECK-LABEL: memset_alloca:
 ; NO-BULK-MEM-NOT: memory.fill
 ; BULK-MEM-NEXT: .functype memset_alloca (i32) -> ()
 ; BULK-MEM-NEXT: global.get $push[[L0:[0-9]+]]=, __stack_pointer
-; BULK-MEM-NEXT: i32.const $push[[L1:[0-9]+]]=, 16
+; BULK-MEM-NEXT: i32.const $push[[L1:[0-9]+]]=, 112
 ; BULK-MEM-NEXT: i32.sub $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]
-; BULK-MEM-NEXT: i32.const $push[[L3:[0-9]+]]=, 6
+; BULK-MEM-NEXT: i32.const $push[[L3:[0-9]+]]=, 12
 ; BULK-MEM-NEXT: i32.add $push[[L4:[0-9]+]]=, $pop[[L2]], $pop[[L3]]
-; BULK-MEM-NEXT: i32.const $push[[L5:[0-9]+]]=, 10
+; BULK-MEM-NEXT: i32.const $push[[L5:[0-9]+]]=, 100
 ; BULK-MEM-NEXT: memory.fill 0, $pop[[L4]], $0, $pop[[L5]]
 ; BULK-MEM-NEXT: return
 define void @memset_alloca(i8 %val) {
-  %a = alloca [10 x i8]
-  %p = bitcast [10 x i8]* %a to i8*
-  call void @llvm.memset.p0i8.i32(i8* %p, i8 %val, i32 10, i1 false)
+  %a = alloca [100 x i8]
+  %p = bitcast [100 x i8]* %a to i8*
+  call void @llvm.memset.p0i8.i32(i8* %p, i8 %val, i32 100, i1 false)
   ret void
 }