From bf5ce04b24936a5b68223a0bfcbef5cb395c4951 Mon Sep 17 00:00:00 2001 From: gingerBill Date: Sun, 31 May 2020 13:50:17 +0100 Subject: Improve rules for shifting behaviour Example: x: u64 = 123; assert(x >> 64 == 0); // In C this would be 123 because (64 & 0b111111) == 0 a: u64 123; assert(a << 64 == 0); // In C this would be 123 because (64 & 0b111111) == 0 --- src/llvm_backend.cpp | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-) (limited to 'src/llvm_backend.cpp') diff --git a/src/llvm_backend.cpp b/src/llvm_backend.cpp index 4266d5921..b064378b6 100644 --- a/src/llvm_backend.cpp +++ b/src/llvm_backend.cpp @@ -5546,17 +5546,39 @@ handle_op: res.value = LLVMBuildXor(p->builder, lhs.value, rhs.value, ""); return res; case Token_Shl: - rhs = lb_emit_conv(p, rhs, lhs.type); - res.value = LLVMBuildShl(p->builder, lhs.value, rhs.value, ""); - return res; + { + rhs = lb_emit_conv(p, rhs, lhs.type); + LLVMValueRef lhsval = lhs.value; + LLVMValueRef bits = rhs.value; + + LLVMValueRef max = LLVMConstInt(lb_type(p->module, rhs.type), 8*type_size_of(lhs.type) - 1, false); + + LLVMValueRef less_equal_width = LLVMBuildICmp(p->builder, LLVMIntULE, bits, max, ""); + + res.value = LLVMBuildShl(p->builder, lhsval, bits, ""); + LLVMValueRef zero = LLVMConstNull(lb_type(p->module, lhs.type)); + res.value = LLVMBuildSelect(p->builder, less_equal_width, res.value, zero, ""); + return res; + } case Token_Shr: - if (is_type_unsigned(type)) { - res.value = LLVMBuildLShr(p->builder, lhs.value, rhs.value, ""); + { + rhs = lb_emit_conv(p, rhs, lhs.type); + LLVMValueRef lhsval = lhs.value; + LLVMValueRef bits = rhs.value; + bool is_unsigned = is_type_unsigned(type); + + LLVMValueRef max = LLVMConstInt(lb_type(p->module, rhs.type), 8*type_size_of(lhs.type) - 1, false); + + LLVMValueRef less_equal_width = LLVMBuildICmp(p->builder, LLVMIntULE, bits, max, ""); + + bits = LLVMBuildSelect(p->builder, less_equal_width, bits, max, ""); + if (is_unsigned) { + res.value = LLVMBuildLShr(p->builder, lhs.value, bits, ""); + } else { + res.value = LLVMBuildAShr(p->builder, lhsval, bits, ""); + } return res; } - rhs = lb_emit_conv(p, rhs, lhs.type); - res.value = LLVMBuildAShr(p->builder, lhs.value, rhs.value, ""); - return res; case Token_AndNot: { LLVMValueRef new_rhs = LLVMBuildNot(p->builder, rhs.value, ""); -- cgit v1.2.3