compiler: combine struct padding zeroing logic

Author: dgryski

compiler/map.go

@@ -288,8 +288,6 @@ func (b *builder) zeroUndefBytes(llvmType llvm.Type, ptr llvm.Value) error {
 		llvmArrayType := llvmType
 		llvmElemType := llvmType.ElementType()
 
-		zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
-
 		for i := 0; i < llvmArrayType.ArrayLength(); i++ {
 			idx := llvm.ConstInt(b.uintptrType, uint64(i), false)
 			elemPtr := b.CreateInBoundsGEP(llvmArrayType, ptr, []llvm.Value{zero, idx}, "")
@@ -312,29 +310,24 @@ func (b *builder) zeroUndefBytes(llvmType llvm.Type, ptr llvm.Value) error {
 			b.zeroUndefBytes(llvmElemType, elemPtr)
 
 			// zero any padding bytes before the next field, if any
+			offset := b.targetData.ElementOffset(llvmStructType, i)
+			storeSize := b.targetData.TypeStoreSize(llvmElemType)
+			fieldEndOffset := offset + storeSize
+
+			var nextOffset uint64
 			if i < numFields-1 {
-				offset := b.targetData.ElementOffset(llvmStructType, i)
-				nextOffset := b.targetData.ElementOffset(llvmStructType, i+1)
-				if storeSize := b.targetData.TypeStoreSize(llvmElemType); offset+storeSize != nextOffset {
-					n := llvm.ConstInt(b.uintptrType, nextOffset-(offset+storeSize), false)
-					llvmStoreSize := llvm.ConstInt(b.uintptrType, storeSize, false)
-					elemPtr = b.CreateBitCast(elemPtr, b.i8ptrType, "")
-					paddingStart := b.CreateInBoundsGEP(b.i8ptrType, elemPtr, []llvm.Value{llvmStoreSize}, "")
-					b.createRuntimeCall("memzero", []llvm.Value{paddingStart, n}, "")
-				}
+				nextOffset = b.targetData.ElementOffset(llvmStructType, i+1)
+			} else {
+				// Last field?  Next offset is the total size of the allcoate struct.
+				nextOffset = b.targetData.TypeAllocSize(llvmStructType)
 			}
-		}
 
-		// zero any padding bytes between end of last field and end of struct
-		allocSize := b.targetData.TypeAllocSize(llvmStructType)
-		lastElemOffset := b.targetData.ElementOffset(llvmStructType, numFields-1)
-		lastElemStore := b.targetData.TypeStoreSize(llvmElementTypes[numFields-1])
-
-		if allocSize != lastElemOffset+lastElemStore {
-			n := llvm.ConstInt(b.uintptrType, allocSize-(lastElemOffset+lastElemStore), false)
-			llvmStoreSize := llvm.ConstInt(b.uintptrType, lastElemOffset+lastElemStore, false)
-			paddingStart := b.CreateInBoundsGEP(b.ctx.Int8Type(), ptr, []llvm.Value{llvmStoreSize}, "")
-			b.createRuntimeCall("memzero", []llvm.Value{paddingStart, n}, "")
+			if fieldEndOffset != nextOffset {
+				n := llvm.ConstInt(b.uintptrType, nextOffset-fieldEndOffset, false)
+				llvmStoreSize := llvm.ConstInt(b.uintptrType, storeSize, false)
+				paddingStart := b.CreateInBoundsGEP(b.i8ptrType, elemPtr, []llvm.Value{llvmStoreSize}, "")
+				b.createRuntimeCall("memzero", []llvm.Value{paddingStart, n}, "")
+			}
 		}
 	}
 

compiler/testdata/zeromap.ll

@@ -33,7 +33,7 @@ entry:
   store %main.hasPadding %2, ptr %hashmap.key, align 8
   %3 = getelementptr inbounds ptr, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %3, i32 3, ptr undef) #4
-  %4 = getelementptr inbounds i8, ptr %hashmap.key, i32 9
+  %4 = getelementptr inbounds { i1, i32, i1 }, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %4, i32 3, ptr undef) #4
   %5 = call i1 @runtime.hashmapBinaryGet(ptr %m, ptr nonnull %hashmap.key, ptr nonnull %hashmap.value, i32 4, ptr undef) #4
   call void @llvm.lifetime.end.p0(i64 12, ptr nonnull %hashmap.key)
@@ -71,7 +71,7 @@ entry:
   store %main.hasPadding %2, ptr %hashmap.key, align 8
   %3 = getelementptr inbounds ptr, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %3, i32 3, ptr undef) #4
-  %4 = getelementptr inbounds i8, ptr %hashmap.key, i32 9
+  %4 = getelementptr inbounds { i1, i32, i1 }, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %4, i32 3, ptr undef) #4
   call void @runtime.hashmapBinarySet(ptr %m, ptr nonnull %hashmap.key, ptr nonnull %hashmap.value, ptr undef) #4
   call void @llvm.lifetime.end.p0(i64 12, ptr nonnull %hashmap.key)
@@ -106,11 +106,11 @@ entry:
   store %main.hasPadding %s.elt9, ptr %hashmap.key.repack8, align 4
   %0 = getelementptr inbounds ptr, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %0, i32 3, ptr undef) #4
-  %1 = getelementptr inbounds i8, ptr %hashmap.key, i32 9
+  %1 = getelementptr inbounds %main.hasPadding, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %1, i32 3, ptr undef) #4
   %2 = getelementptr inbounds [2 x %main.hasPadding], ptr %hashmap.key, i32 0, i32 1, i32 1
   call void @runtime.memzero(ptr nonnull %2, i32 3, ptr undef) #4
-  %3 = getelementptr inbounds i8, ptr %hashmap.key, i32 21
+  %3 = getelementptr inbounds [2 x %main.hasPadding], ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %3, i32 3, ptr undef) #4
   %4 = call i1 @runtime.hashmapBinaryGet(ptr %m, ptr nonnull %hashmap.key, ptr nonnull %hashmap.value, i32 4, ptr undef) #4
   call void @llvm.lifetime.end.p0(i64 24, ptr nonnull %hashmap.key)
@@ -145,11 +145,11 @@ entry:
   store %main.hasPadding %s.elt9, ptr %hashmap.key.repack8, align 4
   %0 = getelementptr inbounds ptr, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %0, i32 3, ptr undef) #4
-  %1 = getelementptr inbounds i8, ptr %hashmap.key, i32 9
+  %1 = getelementptr inbounds %main.hasPadding, ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %1, i32 3, ptr undef) #4
   %2 = getelementptr inbounds [2 x %main.hasPadding], ptr %hashmap.key, i32 0, i32 1, i32 1
   call void @runtime.memzero(ptr nonnull %2, i32 3, ptr undef) #4
-  %3 = getelementptr inbounds i8, ptr %hashmap.key, i32 21
+  %3 = getelementptr inbounds [2 x %main.hasPadding], ptr %hashmap.key, i32 1
   call void @runtime.memzero(ptr nonnull %3, i32 3, ptr undef) #4
   call void @runtime.hashmapBinarySet(ptr %m, ptr nonnull %hashmap.key, ptr nonnull %hashmap.value, ptr undef) #4
   call void @llvm.lifetime.end.p0(i64 24, ptr nonnull %hashmap.key)