LLVM: be sure to never pass align(0) attribute

andrewrk · andrewrk · commit f1757e3b115a · 2022-06-30T16:38:54.000-07:00
This can happen with pointers to zero-bit types.

This commit fixes an LLVM assertion being tripped.
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
@@ -768,7 +768,11 @@ pub const Object = struct {
                             if (ptr_info.@"align" != 0) {
                                 dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.@"align");
                             } else {
-                                dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.pointee_type.abiAlignment(target));
+                                const elem_align = @maximum(
+                                    ptr_info.pointee_type.abiAlignment(target),
+                                    1,
+                                );
+                                dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", elem_align);
                             }
                         }
                     }
@@ -840,7 +844,8 @@ pub const Object = struct {
                     if (ptr_info.@"align" != 0) {
                         dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.@"align");
                     } else {
-                        dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.pointee_type.abiAlignment(target));
+                        const elem_align = @maximum(ptr_info.pointee_type.abiAlignment(target), 1);
+                        dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", elem_align);
                     }
                     const ptr_param = llvm_func.getParam(llvm_arg_i);
                     llvm_arg_i += 1;

Original file line number	Diff line number	Diff line change
`@@ -768,7 +768,11 @@ pub const Object = struct {`
`768`	`768`	`if (ptr_info.@"align" != 0) {`
`769`	`769`	`dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.@"align");`
`770`	`770`	`} else {`
`771`		`- dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.pointee_type.abiAlignment(target));`
	`771`	`+ const elem_align = @maximum(`
	`772`	`+ ptr_info.pointee_type.abiAlignment(target),`
	`773`	`+ 1,`
	`774`	`+ );`
	`775`	`+ dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", elem_align);`
`772`	`776`	`}`
`773`	`777`	`}`
`774`	`778`	`}`
`@@ -840,7 +844,8 @@ pub const Object = struct {`
`840`	`844`	`if (ptr_info.@"align" != 0) {`
`841`	`845`	`dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.@"align");`
`842`	`846`	`} else {`
`843`		`- dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", ptr_info.pointee_type.abiAlignment(target));`
	`847`	`+ const elem_align = @maximum(ptr_info.pointee_type.abiAlignment(target), 1);`
	`848`	`+ dg.addArgAttrInt(llvm_func, llvm_arg_i, "align", elem_align);`
`844`	`849`	`}`
`845`	`850`	`const ptr_param = llvm_func.getParam(llvm_arg_i);`
`846`	`851`	`llvm_arg_i += 1;`